Notes: Unit 3 - Measurement and Scaling Techniques
Notes: Unit 3 - Measurement and Scaling Techniques
                             Objectives
                                  	 Explain	the	concepts	of	measurement	and	scaling
                                  	 Discuss	four	levels	of	measurement	scales
                                  	 Classify	and	discuss	different	scaling	techniques
                             3.1 Introduction
                                 As	we	discussed	earlier,	the	data	consists	of	quantitative	variables	like	price,	income,	
                             sales	 etc.,	 and	 qualitative	 variables	 like	 knowledge,	 performance,	 character	 etc.	 The	
                             qualitative	information	must	be	converted	into	numerical	form	for	further	analysis.	This	is	
                             possible	through	measurement	and	scaling	techniques.	A	common	feature	of	survey	based	
                             research	is	to	have	respondent’s	feelings,	attitudes,	opinions,	etc.	in	some	measurable	
                             form.	 For	 example,	 a	 bank	 manager	 may	 be	 interested	 in	 knowing	 the	 opinion	 of	 the	
                             customers	about	the	services	provided	by	the	bank.	Similarly,	a	fast	food	company	having	a	
                             network in a city may be interested in assessing the quality and service provided by them.
                             As	a	researcher	you	may	be	interested	in	knowing	the	attitude	of	the	people	towards	the	
                             government	announcement	of	a	metro	rail	in	Delhi.	In	this	unit	we	will	discuss	the	issues	
                             related	 to	 measurement,	 different	 levels	 of	 measurement	 scales,	 and	 various	 types	 of	
                             scaling	techniques	and	also	selection	of	an	appropriate	scaling	technique.
                                 The	most	important	aspect	of	measurement	is	the	specification	of	rules	for	assigning	
                             numbers	to	characteristics.	The	rules	for	assigning	numbers	should	be	standardized	and	
                             applied	uniformly.	This	must	not	change	over	time	or	objects.
     of	 attributes	 allow	 the	 researcher	 more	 scope	 for	 further	 processing	 of	 data	 and	
statistical analysis.
     a) Nominal Scale is the crudest among all measurement scales but it is also the
simplest	 scale.	 In	 this	 scale	 the	 different	 scores	 on	 a	 measurement	 simply	 indicate	
different	 categories.	 The	 nominal	 scale	 does	 not	 express	 any	 values	 or	 relationships	
between	variables.	For	example,	labeling	men	as	‘1’	and	women	as	‘2’	which	is	the	most	
common	way	of	labeling	gender	for	data	recording	purpose	does	not	mean	women	are	
‘twice	something	or	other’	than	men.	Nor	it	suggests	that	men	are	somehow	‘better’	than	
women.	Another	example	of	nominal	scale	is	to	classify	the	respondent’s	income	into	three	
groups:	the	highest	income	as	group	1.	The	middle	income	as	group	2,	and	the	low-income	
as	group	3.	The	nominal	scale	is	often	referred	to	as	a	categorical	scale.	The	assigned	
numbers	have	no	arithmetic	properties	and	act	only	as	labels.	The	only	statistical	operation	
that	can	be	performed	on	nominal	scales	is	a	frequency	count.	We	cannot	determine	an	
average except mode. In designing and developing a questionnaire, it is important that the
response categories must include all possible responses. In order to have an exhaustive
number	of	responses,	you	might	have	to	include	a	category	such	as	‘others’,	‘uncertain’,	
‘don’t	know’,	or	‘can’t	remember’	so	that	the	respondents	will	not	distort	their	information	
by	forcing	their	responses	in	one	of	the	categories	provided.	Also,	you	should	be	careful	
and be sure that the categories provided are mutually exclusive so that they do not overlap
or get duplicated in any way.
    b) Ordinal Scale	involves	the	ranking	of	items	along	the	continuum	of	the	characteristic	
being	scaled.	In	this	scale,	the	items	are	classified	according	to	whether	they	have	more	or	
less	of	a	characteristic.	The	main	characteristic	of	the	ordinal	scale	is	that	the	categories	
have	 a	 logical	 or	 ordered	 relationship.	This	 type	 of	 scale	 permits	 the	 measurement	 of	
degrees	of	difference,	(that	is,	‘more’	or	‘less’)	but	not	the	specific	amount	of	differences	
(that	is,	how	much	‘more’	or	‘less’).	This	scale	is	very	common	in	marketing,	satisfaction	
and attitudinal research.
                                 Ordinal	measurements	do	not	provide	information	on	how	much	more	or	less	of	the	
                             characteristic	various	objects	possess.	For	example,	if	in	respect	of	a	certain	characteristic	
         Notes
                             two objects have the ranks 5 and 8 and two other objects the ranks 3 and 6, we cannot
                             say	that	the	differences	between	the	two	pairs	are	equal.	There	is	also	no	way	to	know	
                             that	any	object	has	none	of	the	characteristic	being	measured.
                                  The	kind	of	descriptive	statistics	that	can	be	calculated	from	these	data	are	mode,	
                             median	 and	 percentages.	 For	 example,	 in	 the	 following	 table	 which	 shows	 the	 quality	
                             ratings	given	by	600	housewives	to	one	brand	of	coffee	one	can	usefully	calculate	the	
                             median and modal quality
                                 ratings.	Both	are	‘2’	in	this	case.	One	can	also	calculate	the	percentages	of	the	total	
                             appearing	in	each	rank.	But	it	is	meaningless	to	calculate	a	mean	because	the	differences	
                             between ordinals scales values are not necessarily, the same.
                                  c) Interval Scale is a scale in which the numbers are used to rank attributes such that
                             numerically equal distances on the scale represent equal distance in the characteristic
                             being	measured.	An	interval	scale	contains	all	the	information	of	an	ordinal	scale,	but	it	
                             also	one	allows	to	compare	the	difference/distance	between	attributes.	For	example,	the	
                             difference	between	‘1’	and	‘2’	is	equal	to	the	difference	between	‘3’	and	‘4’.	Further,	the	
                             difference	between	‘2’	and	‘4’	is	twice	the	difference	between	‘1’	and	‘2’.	However,	in	an	
                             interval	scale,	the	zero	point	is	arbitrary	and	is	not	true	zero.	This,	of	course,	has	implications	
                             for	the	type	of	data	manipulation	and	analysis.	We	can	carry	out	on	data	collected	in	this	
                             form.	It	is	possible	to	add	or	subtract	a	constant	to	all	of	the	scale	values	without	affecting	
                             the	form	of	the	scale	but	one	cannot	multiply	or	divide	the	values.	Measuring	temperature	
                             is	an	example	of	interval	scale.	We	cannot	say	400C	is	twice	as	hot	as	200C.	The	reason	
                             for	this	is	that	00C	does	not	mean	that	there	is	no	temperature,	but	a	relative	point	on	the	
                             Centigrade	Scale.	Due	to	lack	of	an	absolute	zero	point,	the	interval	scale	does	not	allow	
                             the conclusion that 400C is twice as hot as 200C.
                                 d) Ratio Scale	is	the	highest	level	of	measurement	scales.	This	has	the	properties	of	
                             an	interval	scale	together	with	a	fixed	(absolute)	zero	point.	The	absolute	zero	point	allows	
                             us	to	construct	a	meaningful	ratio.	Examples	of	ratio	scales	include	weights,	lengths	and	
                             times.	In	the	marketing	research,	most	counts	are	ratio	scales.	For	example,	the	number	of	
                             customers	of	a	bank’s	ATM	in	the	last	three	months	is	a	ratio	scale.	This	is	because	you	can	
                             compare this with previous three months. Ratio scales permit the researcher to compare
                             both	differences	in	scores	and	relative	magnitude	of	scores.	For	example,	the	difference	
                             between	10	and	15	minutes	is	the	same	as	the	difference	between	25	and	30	minutes	
                             and	30	minutes	is	twice	as	long	as	15	minutes.	Most	financial	research	that	deals	with	
                             rupee	values	utilizes	ratio	scales.	However,	for	most	behavioral	research,	interval	scales	
                             are	typically	the	highest	form	of	measurement.	Most	statistical	data	analysis	procedures	
                             do	not	distinguish	between	the	interval	and	ratio	properties	of	the	measurement	scales	
                             and	it	is	sufficient	to	say	that	all	the	statistical	operations	that	can	be	performed	on	interval	
                             scale	can	also	be	performed	on	ratio	scales.
                                  With	a	ratio	measurement,	the	comparison	between	ratios	of	the	absolute	magnitude	
                             of	the	numbers	becomes	possible.	Thus,	a	person	weighing	100kg	.	is	said	to	be	twice	as	
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Research Methodology                                                                                                        29
heavy as one weighing 50kg. and a person weighing 150kg is three times as heavy. Further,
with a ratio scale we can compare intervals, rank objects according to magnitude, or use
                                                                                                           Notes
the	numbers	to	identify	the	objects.	All	descriptive	measures	and	inferential	techniques	
are	applicable	to	ratio-measured	data.
Comparative Scale
    a) Paired Comparison Scale:	This	is	a	comparative	scaling	technique	in	which	a	
respondent	is	presented	with	two	objects	at	a	time	and	asked	to	select	one	object	(rate	
between	two	objects	at	a	time)	according	to	some	criterion.
Scaling Technique
     b) Rank Order Scale: This	is	another	type	of	comparative	scaling	technique	in	which	
respondents are presented with several items simultaneously and asked to rank them
in	the	order	of	priority.	This	is	an	ordinal	scale	that	describes	the	favored	and	unfavored	
objects, but does not reveal the distance between the objects.
    c) Constant Sum Scale: In this scale, the respondents are asked to allocate a constant
sum	of	units	such	as	points,	rupees,	or	chips	among	a	set	of	stimulus	objects	with	respect	
to some criterion.
      d) Q-Sort Scale:	This	is	a	comparative	scale	that	uses	a	rank	order	procedure	to	sort	
objects	based	on	similarity	with	respect	to	some	criterion.	The	important	characteristic	
of	 this	 methodology	 is	 that	 it	 is	 more	 important	 to	 make	 comparisons	 among	 different	
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30                                                                                                             Research Methodology
                             responses	of	a	respondent	than	the	responses	between	different	respondents.	Therefore,	
                             it	is	a	comparative	method	of	scaling	rather	than	an	absolute	rating	scale.	In	this	method	
         Notes               the	respondent	is	given	statements	in	a	large	number	for	describing	the	characteristics	of	
                             a	product	or	a	large	number	of	brands	of	a	product.
                             Non-Comparative Scale
                                The	non-comparative	scaling	techniques	can	be	further	divided	into:	
                                      Likert scale: In Likert scale, the respondents indicate their own attitudes by
                                       checking	how	strongly	they	agree	or	disagree	with	carefully	worded	statements	
                                       that	 range	 from	 very	 positive	 to	 very	 negative	 towards	 the	 attitudinal	 object.	
                                       Respondents	generally	choose	from	five	alternatives	(say	strongly	agree,	agree,	
                                       neither	agree	nor	disagree,	disagree,	strongly	disagree).
                                  	 Semantic	 Differential	 Scale:	This	 is	 a	 seven	 point	 rating	 scale	 with	 end	 points	
                                       associated	with	bipolar	labels	(such	as	good	and	bad,	complex	and	simple)	that	
                                       have	semantic	meaning.	The	Semantic	Differential	scale	is	used	for	a	variety	of	
                                       purposes.	It	can	be	used	to	find	whether	a	respondent	has	a	positive	or	negative	
                                       attitude towards an object. It has been widely used in comparing brands, products
                                       and company images. It has also been used to develop advertising and promotion
                                       strategies and in a new product development study.
                                  	 Staple	Scale:	The	Stapel	scale	was	originally	developed	to	measure	the	direction	
                                       and	intensity	of	an	attitude	simultaneously.	Modern	versions	of	the	Stapel	scale	
                                       place	 a	 single	 adjective	 as	 a	 substitute	 for	 the	 Semantic	 differential	 when	 it	 is	
                                       difficult	to	create	pairs	of	bipolar	adjectives.	The	modified	Stapel	scale	places	a	
                                       single	adjective	in	the	centre	of	an	even	number	of	numerical	values	(say,	+3,	
                                       +2,	+1,	0,	-1,	-2,	-3).	This	scale	measures	how	close	to	or	how	distant	from	the	
                                       adjective a given stimulus is perceived to be.
How satisfied you are with the brand- X detergent that you are presently using?
    Completely
    dissatisfied
    This	is	a	non-comparative	scale	since	it	deals	with	a	single	concept	(the	brand	of	a	
detergent).	On	the	other	hand,	a	comparative	scale	asks	a	respondent	to	rate	a	concept.	
For example, you may ask:
Brand-X Brand-Y
    	 In	 this	 example	 you	 are	 comparing	 one	 brand	 of	 detergent	 with	 another	 brand.	
Therefore,	 in	 many	 situations,	 comparative	 scaling	 presents	 ‘the	 ideal	 situation’	 as	 a	
reference	for	comparison	with	actual	situation.
3.6 Summary
    The	 issues	 related	 to	 measurement,	 different	 levels	 of	 measurement	 scales,	 and	
various	types	of	scaling	techniques	and	also	selection	of	an	appropriate	scaling	technique	
are important to understand the research analysis and in decision making.
                             1.	Which	one	is	the	crudest	and	simplest	measuring	scale	among	them?
                                  a)	 Nominal
                                  b)	 Ordinal
                                  c)	 Interval
                                  d)	 Ration
                             4. Which scale has seven point rating scale with end points associated with bipolar labels
                                 (such	as	good	and	bad,	complex	and	simple)	that	have	semantic?
                                  a)	 Staple	scale
                                  b)	 Rating	scale
                                  c)	 Likert	scale
                                  d)	 Semantic		difference	scale
10.	This	is	a	comparative	scaling	technique	in	which	a	respondent	is	presented	with	two	
    objects	at	a	time	and	asked	to	select	one	object	(rate	between	two	objects	at	a	time)	
    according to some criterion.
    a)	 Rank	order	scale
    b)	 Q-sort	scale
    c)	 Paired	comparison
    d)	 Constant	sum
Questions &Exercises
1. What is measurement?
5. What is semantic differential scale? For what purpose is this scale used?
                             8.	 What	 are	 the	 differences	 between	 the	 Stapel	 scale	 and	 the	 semantic	 differential?	
         Notes                   Which	scale	is	more	popular?
9. What are the major decisions involved in constructing an itemized rating scale?
                             10.	 What	are	the	differences	between	the	following	scaling	techniques,	and	how	would	
                                  you	select	a	particular	technique?
                                      balanced and unbalanced scales
                                  	 forced	and	non-forced	scales
Objectives
    	    To	understand		what	is	questionnaire	and	its	objectives	
    	    To	understand	the	various	steps	involved	in	the	questionnaire	designing	including	
          content	of	the	questionnaire,	wording	,	sequence	,whom	to	ask	,what	to	say		etc	
    	    To	consider	the	guidelines	that	must	be	followed	at	each	step.
    	    To	understand	the	ethical	issues	involved	in	questionnaire	design	
4.1 Introduction
     A	 questionnaire	 is	 a	 formalized	 set	 of	 questions	 for	 obtaining	 information	 from	
respondents.		It	is	the	basic	research	tool	and	can	be	described	as	a	collection	of	formalized	
set	 of	 questions	 -	 drawn	 up	 with	 the	 research	 problem	 in	 mind	 -	 used	 for	 obtaining	
information	from	the	respondents	for	finding	solutions	to	the	research	problem.																							
                             in	mind	the	target	respondents	.The	respondents	should	at	least	know	the	type	and	
                             the	level	of	expected	questions	expected	.Questions	seeking	specific	details	about	
         Notes               the	data	and	time	of	events	should	be	avoided.	Care	must	be	taken	in	designing	the	
                             questions	seeking	information	or	personal	facts	such	as	sex,	life,	bad	habits	or	status	
                             symbol	.A	single	question	may	be	split	into	multiple	questions	for	better	response	from	
                             the respondents.
                                Thus,	 following	 points	 must	 be	 considered	 while	 deciding	 on	 the	 content	 of	 the	
                             questionnaire:
“Do you think Coca-Cola is a tasty and refreshing soft drink?” (Incorrect)
                             Context
                                 Respondents are unwilling to respond to questions which they consider to be
                                    inappropriate	for	the	given	context.		
                                  	 The	researcher	should	manipulate	the	context	so	that	the	request	for	information	
                                       seems appropriate.
Sensitive Information
   	 Respondents	are	unwilling	to	disclose,	at	least	accurately,	sensitive	information	
        because	this	may	cause	embarrassment	or	threaten	the	respondent’s	prestige	or	
        self-image.	
    	 Please	list	all	the	departments	from	which	you	purchased	merchandise	on	your	
        most	recent	shopping	trip	to	a	department	store.	(Incorrect)
    	 In	the	list	that	follows,	please	check	all	the	departments	from	which	you	purchased	
        merchandise on your most recent shopping trip to a department store.
    1.	Women’s	dresses	                     ____
4. Cosmetics ____
16. Jewelry
    1.	 Open-ended	questions
    2.	 Multiple	choice	Questions
    3. Dichotomous Questions
     Open -ended questions :	It	requires	the	respondents	to	express	freely	their	views/
ideas		in	their	own	words	.the	degree	of	openness	varies	from	question	to	question	.For	
example	,the	question	“What	do	you	think	about		the	ice	cream	?”	gives	the	respondents	
total	freedom	to	talk	about	on	any	brand	,flavor	etc	.
Advantages:
   1.	 It	avoids	persuading	the	respondents	with	a	pre	-stated	set	of	response	categories.
                                  3.	 Open-ended	questions	provide	the	basis	for	the	researcher	to	judge	the	actual	
         Notes                        values	and	the	views	of	the	respondents.	
                             Disadvantages:
                                1.	 It	is	more	time	-consuming	
                                  2.	 The	response	obtained	maybe	so	varied		that	it	may	be	impossible	to	arrive	at	a	
                                      conclusion
                                  3.	 Coding	or	categorizing	the	respondent’s	answers	is	a	very	costly	and	laborious	
                                      act
                                 			Multiple	Choice	Questions:		The	questions	for	which	we	have	a	number	of	choices	
                             as	answer	are	called	multiple	choice	questions.	The	question	may	be	provided	with	two	or	
                             more	options	and	the	respondents	is	to	select	any	one	of	them	which	he	thinks	is	the	best.
                             Advantages:
                                1.	 It	is	easier	for	both	the	interviewer	and	the	respondents	
                                  2.	 It	 tends	 to	 reduce	 the	 interviewer	 bias	 and	 bias	 caused	 by	 varying	 levels	 of	
                                      respondents articulation
                                  3.	 The	tabulation	and	analysis	in	multiple	choice	questions	is	much	simpler.
                             Disadvantages:
                                1.	 To	develop	a	sound	set	of	multiple	choice	questions	considerable	effort	is	required	
                                  2.	 The	list	of	potential	answers	can	cause	several	types	of	distortions	in	the	resulting	
                                      data
                                  3.	 Too	many	questions	and	choices	make	the	questionnaire	monotonous.
                             Dichotomous Questions:
                                 A question having two possible responses is considered to be dichotomous.
                             Dichotomous	questions	are	often	used	in	surveys	that	ask	for	a	Yes/No,	True/False				or	
                             Agree/Disagree	response.	Often,	the	two	alternatives	of	interest	are	supplemented	by	a	
                             neutral	alternative,	such	as	“no	opinion,”	“don’t	know,”	“both,”	or	“none.”		
                             e) Wording of Questionnaire
                                 Question	wording	can	be	defined	as	the	translation	of	the	desired	question	content	
                             and structure into words that the respondent can clearly and easily understand. Question
                             wording	is	the	most	complex,	critical	and	difficult	task	in	designing	a	questionnaire
                                  	 Item	Non-Response:	Error	arising	due	to	poor	question	wording	and	subsequent	
                                       low	quality	response	from	the	respondent.
                                  	 Response	Error:	Error	arising	due	to	divergence	in	interpretation	of	the	question	
                                       by the respondent and the interviewer
                                 Define	 the	 Issues	As	 Clearly	As	 Possible.	 The	 issues	 or	 the	 objectives	 should	 be	
                             defined	as	clearly	as	possible,	for	example--
    In	 the	 above	 example	 we	 can	 see,	 in	 the	 first	 question	 the	 options	 given	 can	 be	
misinterpreted	by	the	responded	as	each	responded	can	have	a	different	meaning	to	the	
words	given	like	sometimes,	often	regularly	but	in	the	second	question	the	options	are	
specific	and	measureable	and	doesn’t	lead	to	any	ambiguity	or	confusion.
                                  	 The	question	being	branched	should	be	placed	as	close	as	possible	to	the	question	
                                       causing	the	branching,	and	(2)	the	branching	questions	should	be	ordered	so	that	
         Notes
                                       the	respondents	cannot	anticipate	what	additional	information	will	be	required.
Summary
    Questionnaire	is	one	of	the	most	important	tools	to	collect	the	quantitative	data.	It	
must	translate	the	information	needed	into	a	set	of	specific	questions	that	the	respondents	
can and will answer. It must motivate the respondents to respond and must also help in
reducing	the	errors.	The	designing	of	a	questionnaire	is	an	art	.The	first	and	the	foremost	
step	is	to	analyze	the	information	needed	and	the	type	of	the	interviewing	method	.the	next	
step	is	to	decide	on	the	content	of	the	questionnaire.	The	question	should	overcome	the	
respondent’s	inability	and	unwillingness	to	answer.	Then	comes	the	decision	regarding	
the	structure	of	the	questions	.The	questions	can	be	structured	or	unstructured.
   Determining	the	wording	of	the	questions	involves	defining	the	issues,	using	ordinary	
words, using unambiguous words and using the dual statements. Once the questions
have been worded, the order in which they will be asked should be decided. Special
considerations	should	be	given	to	the	opening	questions,	type	of	the	information,	difficult	
questions,	and	the	effect	of	the	subsequent	questions.	A	logical	order	should	be	maintained.
    Next	 step	 is	 of	 determining	 the	 form	 and	 the	 layout	 of	 the	 questionnaire	 .The	
questionnaire	 should	 be	 easy	 to	 read	 and	 well	 formatted.	 Last	 step	 is	 the	 pretesting.	
Moreover,	several	ethical	issues	related	to	the	researcher-respondent	relationship	and	
the	researcher-client	relationship	may	have	to	be	addressed.	Use	of	IT	can	also	help	the	
researcher in designing a sound questionnaire
2.	 Which	type	of	questionnaire	tends	to	reduce	the	interviewer	bias	and	bias	caused	by	
    varying	levels	of	respondent’s	articulation,	also	the	simplest	to	analyze	data?
    a)	 Open-ended	questions
    b)	 Multiple	choice	Questions
                                  c)	 Dichotomous	Questions	
         Notes                    d)	 Close	ended	question
                             4.	 _____________	is	one	of	the	most	important	tools	to	collect	the	quantitative	data.
                                  a)	 Sampling	technique	
                                  b)	 Scaling	method
                                  c)	 Questionnaire
                                  d)	 Experimental	method
                             5.	 Before	designing	a	questionnaire,	what	is	the	prime	thing	one	should	considered?
                                  a)	 Content	of	the	questionnaire
                                  b)	 Structure	of	the	questionnaire
                                  c)	 Type	of	the	questionnaire
                                  d)	 Information		needed
                             8.	 What	 is	 the	 most	 complex,	 critical	 and	 difficult	 task	 in	 designing	 a	 questionnaire	
                                 structure?
                                  a)	 Sequence	of	questionnaire
                                  b)	 Words	of	questionnaire
                                  c)	 Layout	of	questionnaire
                                  d)	 	Pre-testing	of	questionnaire
Questions &Exercises
1. How will you determine the type of questions to be used in preparing the questionnaire?
3.	 What	are	the	common	mistakes	made	in	the	construction	of	the	questionnaire?		Explain	
    how	that	can	be	avoided?
5.	 Develop	a	questionnaire	for	determining	how	the	students	select	the	restaurants.	Use	
    the	randomized	sampling	technique.
                             Objectives
                                  	 Differentiate	a	sample	from	census	and	identify	the	conditions	that	favor	the	use	
                                       of	sample	versus	a	census
                                      Sampling design Process
                                  	 Classification	of	sampling	technique
                                  	 Description	of	probability	and	non-probability	sampling
                             5.1 Introduction
                                  In	 this	 chapter	 we	 will	 try	 to	 learn	 about	 basic	 concepts	 of	 sampling	 and	 various	
                             techniques	 of	 sampling.	 Sample	 design	 process	 is	 very	 essential	 and	 important	 step	
                             before	 execute	 sampling	 process.	 Classification	 of	 sampling	 helps	 us	 to	 differentiate	
                             various sampling technique and to make them understand. Sampling is stage which is
                             vital	for	market	research,	without	this	we	would	not	be	able	to	start	our	research	process.
    An	 element	 is	 the	 object	 about	 which	 or	 from	 which	 the	 information	 is	 desired.	A	
sampling	unit	is	an	element,	or	a	unit	containing	the	element,	that	is	available	for	selection	
at	some	stage	of	the	sampling	process.
    In	the	Bayesian	approach,	the	elements	are	selected	sequentially.	After	each	element	
is added to the sample, the data are collected, sample statistics computed, and sampling
cost	determined.	This	approach	is	theoretically	appealing.
   In	sampling	with	replacement,	an	element	is	selected	from	the	sampling	frame	and	
appropriate	data	are	obtained.	Then	the	element	is	placed	back	in	the	sampling	frame	and	
appropriate	data	are	obtained.	Then	the	element	is	placed	back	in	the	sampling	frame.
                             In any marketing research project, money and time are limited. Other constraints include
                             the	availability	of	qualified	personnel	for	data	collection.
         Notes
                             Execute the Sampling Process
                                 Execution	of	the	sampling	process	requires	a	detailed	specification	of	how	the	sampling	
                             design	decision	with	respect	to	the	population,	sampling	frame,	sampling	unit,	sampling	
                             technique,	and	sample	size	are	to	be	implemented.	If	households	are	the	sampling	unit,	
                             an	operational	definition	of	a	household	is	needed.
                                  It	relies	on	personal	judgment	of	the	researcher	rather	than	chance	to	select	sample	
                             elements.	The	researcher	can	arbitrarily	or	consciously	decide	what	elements	to	include	
                             in the sample.
                             1. Convenience Sampling
                                 Convenience	 sampling	 attempts	 to	 obtain	 a	 sample	 of	 convenient	 elements.	 The	
                             selection	 of	 sampling	 units	 is	 left	 primarily	 to	 the	 interviewer.	 Often,	 respondents	 are	
                             selected because they happen to be in the right place at the right time.
                             2. Judgmental Sampling
                                 It	is	form	of	convenience	sampling	in	which	the	population	elements	are	selected	based	
                             on	the	judgment	of	researcher.	The	researcher,	exercising	judgment	or	expertise,	choose	
                             the elements to be included in the sample, because they he or she believes that they are
                             representative	of	the	population	of	interest	or	otherwise	appropriate.
                             3. Quota Sampling
                                  It	may	be	viewed	as	two	stages	restricted	judgmental	sampling.	The	first	stage	consists	
                             of	 developing	 control	 categories,	 or	 quotas,	 of	 population	 elements.	 To	 develop	 these	
                             quotas, the researcher lists relevant control characteristics and determines the distribution
                             of	these	characteristics	and	determines	the	distribution	of	these	characteristics	in	the	target	
                             population.	The	relevant	control	characteristics,	which	may	include	sex,	age,	and	race,	
                             are	identified	on	the	basis	of	judgment.
                                 In the second stage, sample elements are selected based on convinces or judgment.
                             Once	quotas	have	been	assigned,	there	is	considerable	freedom	in	selecting	the	elements	
                             to be included in the sample.
    This	process	may	be	carried	out	in	waves	by	obtaining	referrals	from	referrals,	thus	
leading	to	snowballing	effect.	Even	though	probability	sampling	is	used	to	select	the	initial	
respondents,	the	final	sample	is	non	probability	sample.
    In sampling random sampling, each element in the population has a known and
equal	 probability	 of	 selection.	 Furthermore,	 each	 possible	 sample	 of	 a	 given	 size	 has	
a	known	and	equal	probability	of	being	the	sample	actually	selected.	This	implies	that	
every	sample	is	drawn	by	a	random	procedure	from	a	sampling	frame.		To	draw	a	simple	
random	sample,	the	researcher	first	complies	a	sampling	frame	in	which	each	element	is	
assigned	a	unique	identification	number.	Then	numbers	are	generated	to	determine	which	
elements to include in number.
2. Systematic Sampling
    Systematic sampling is similar to SRS in that each population elements has a known
and	equal	probability	of	selection.	It	is	less	costly	and	easier	than	SRS,	because	random	
selection	is	done	daily	basis.	Moreover,	the	random	numbers	do	not	have	to	be	matched	
with	individual	elements	as	in	SRS.	This	reduces	the	cost	of	sampling.
3. Stratified Sampling:
     Stratified	sampling	is	a	two	step	process	in	which	the	population	is	portioned	into	sub	
population	or	strata.	The	strata	should	be	mutually	exclusive	and	collectively	exhaustive	
in that every population element should be assigned to one and only stratum and no
population	element	should	be	omitted.	A	major	objective	of	stratified	sampling	is	to	increase	
precision without increase cost.
    The	criteria	for	the	selection	of	these	variables	consist	of	homogeneity,	heterogeneity,	
relatedness,	 and	 cost.	 The	 elements	 within	 a	 stratum	 should	 be	 as	 homogeneous	 as	
possible,	but	the	elements	in	different	strata	should	be	as	heterogeneous	as	possible.	
4. Cluster Sampling:
     In	cluster	sampling,	the	target	population	is	first	divided	into	mutually	exclusive	and	
collectively	exhaustive	subpopulations	or	clusters.	Then	a	random	sample	of	cluster	is	
selected based on probability sampling techniques such as SRS. For each selected
cluster,	either	all	the	elements	are	included	in	the	sample	or	sample	of	elements	is	drawn	
probabilistically.
                                  If	all	the	elements	in	each	selected	cluster	are	included	in	sample	the	procedure	is	
                             called	one-stage	cluster	sampling.	If	a	sample	of	element	is	drawn	probabilistically	from	
         Notes
                             each selected cluster, the procedure is two stage cluster sampling. A cluster sampling can
                             have multiple stages, as in multistage cluster sampling.
                                Area	sampling	is	a	common	form	of	cluster	sampling	which	the	clusters	consist	of	
                             geographic areas such as counties, blocks.
                                 There	are	two	type	of	two	stage	design;	one	type	involves	SRS	at	the	first	stage	as	
                             well	as	the	second	stage.	This	design	is	called	two	stage	cluster	sampling.
                                                                         Cluster
                                                                        Sampling
                             5.5 Summary
                                  Sampling	is	the	process	of	making	a	selection	of	sampling	elements	from	a	defined	set	
                             of	elements	called	a	population.	A	population	is	defined	as	per	the	marketing	researcher’s	
                             objective	and	research	questions.	Usually	Practical	M.R.	uses	a	multi-stage	selection	of	
                             sampling	units,	until	the	respondent	are	selected	in	the	final	stage	of	sampling	process.
                                  The	formulas	for	sample	size	calculation	can	be	used	as	one	of	the	inputs	for	deciding	
                             on	 the	 final	 sample	 size.	 But	 other	 considerations	 that	 ythe	 researcher	 must	 look	 into	
                             include-the	number	of	cities	or	center	used,	the	criticality	of	the	various	questions	in	the	
                             questionnaire,	cell	size	during	the	analysis	stage,	time	and	budget	constraints,	and	other	
                             issue	based	on	the	researcher’s	experience.	The	important	thing	to	remember	is	that	it	is	
                             not completely a deterministic process, but involves several assumptions and judgments
                             on	the	part	of	the	researcher,	as	detailed	in	the	chapter.
                                  Probability sampling techniques are those in which the researcher knows the probability
                             of	a	sampling	unit	getting	selected	in	the	sample.	In	non-probability	sampling	methods,	no	
                             such	knowledge	of	the	selection	probability	is	possible.	The	popular	probability	sampling	
                             techniques	 are	 simple	 random	 sampling,	 systematic	 sampling,	 stratified	 sampling	 and	
                             cluster	 sampling.	 The	 non-probability	 techniques	 include	 quota	 sampling,	 judgment	
                             sampling, convince sampling, and snowball sampling.
Amity Directorate of Distance & Online Education
Research Methodology                                                                                                       49
    A	sample	is	usually	more	accurate	than	a	census	of	a	large	population	due	to	the	high	
non-sampling	errors	that	occur	in	doing	large	measurements	Sampling	errors	are	those	
                                                                                                          Notes
which occur due to the selection process, and can be estimated and controlled by using
probability	sampling	methods.	Non	sampling	errors	include	human	errors	in	the	way	of	
asking questions, counting data entry or tabulation, and so on. Non sampling error can be
minimized	by	careful	selection	and	training	of	interviewers,	field	control	procedures	and	
avoiding	known	sources	of	such	errors.	Total	error	in	a	research	is	the	sum	of	sampling	
and	 non	 sampling	 errors	 and	 researcher	 should	 minimize	 total	 error	 by	 balancing	 the	
sampling	and	non-sampling	errors.
2.	 Execution	of	the	sampling	process	requires	a	detailed	specification	of	how	the	sampling	
    design	decision	with	respect	to	the-
    a)	 Population
    b)	 Sample	frame
    c)	 Sample	size
    d)	 All	the	above