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Arithmetic Mean
Mean is number which lies
between the highest and the
lowest value. In other words, it
represents the central value of a
group of observations or data.
Mean= Sum of observations/number
of observations.
Mean (frequency
distribution)
1. Multiply each observation (x) by its
corresponding frequency (f) and
denote it by (f *x).
2. Find the sum of all products obtained
above and denote by( f *x).
3. Find the sum of all frequencies and
denote it by f.
4. Divide the sum of all the products by
the sum of all frequencies, i.e., f * x
by f.
Median
The median is the value which is strictly
in the middle of the list of the
observations when written in order of
size. It is also a measure of central
tendency.
Mode
The value which occurs the most is
called mode. In other words, the
value of the observation which has
maximum frequency in a data is
called mode.
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Q
Time!!
1. The mean of 10 numbers is
32. If one number is excluded,
mean of the remaining
numbers becomes 27. Find
the excluded number.
SolutionMean of 10 numbers
=32
Sum of 10 numbers =32*10=320
Mean of 9 numbers =30
Sum of 9 numbers =27*9=243
Excluded number =320-243 = 77
2.
The mean of 7 numbers is 25. If
one number is excluded, mean of
new set of numbers becomes 27.
find the included number.
SolutionMean of 7 numbers =25
Sum of 7 numbers =25*7=175
Mean of 8 numbers =27
Sum of 8 numbers =27*8=216
Included number =216-175=41
3. Calculate the mean for the following
dataHeight
(in cm)
140
142
143
145
148
150
No. of
student
s
10
15
SolutionHeight (x)
Frequency (f)
Product(f*x)
140
142
143
145
148
150
2
6
10
15
4
3
280
852
1430
2175
592
450
Total =
40
5779
Mean= fx / f =5779/40 =144.475
4. Calculate the mean of the following
dataMarks
No. of
student
s
10
11
12
13
14
15
10
SolutionMarks (x)
No. of
students (f)
Product (f*x)
32
45
10
30
11
88
12
48
13
10
130
14
70
15
15
Total =
40
458
Mean= fx / f = 458/40 = 11.45
5. Find the median of 5, 9, 6, 4, 7, 2, 8
SolutionArranging the numbers in ascending
order we get - 2, 4, 5, 6, 7, 8, 9.
There are 7 observations. The middle
(i.e., 7+1/2 th) observation is 6.
Hence median= 6.
6. Find the median of2, 5, 3, 2, 4, 5, 2, 4, 6, 8, 7, 9, 7
SolutionArranging the numbers in ascending order
we get 2, 2, 2, 3, 4, 4, 5, 5, 6, 7, 7, 8, 9.
There are 13 observations. The middle
(i.e.,13+1/2th ) observation is 5.
Hence median= 5
7. Find the median of11, 10, 12, 9, 8, 16, 15, 14
SolutionAfter arranging in ascending order, we get
8, 9, 10, 11, 12, 14, 15, 16.
There are 8 observations. There is no
strict middle observation. Here median is
average of (8/2) 4th and (8/2+1) 5th
observations.
Fourth observation= 11
Fifth observation= 12
Median= 11+12/2 = 11.5
8. Find the median of2, 3, 4, 3, 2, 4, 6, 5, 7, 6, 5, 9, 8,
10
SolutionAfter arranging in ascending order, we
get
2, 2, 3, 3, 4, 4, 5. 5, 6, 6, 7, 8, 9, 10.
Here we have 14 observations. The 7 th
and 8th observation are in the middle.
7th observation = 5
8th observation = 5
Median = 5+5/2 = 5
9. Find the mode-
SolutionCarnation is the mode.
10. Find the mode-
SolutionChocolate bar is the mode.
11. Find the mode-
SolutionThe month of June is the mode.
Efforts
bySaransh
Gautam