Grade 10 - Information Processing 2
Content Outline
● Types of Errors
● Data Verification vs. Validation
● Methods of Data Verification
● Methods of Data Validation
● Methods of File Organization and Access
Types of Errors
There are three (3) types of errors which occur at data entry:
● Transmission Errors: Occur when data transmitted from one device to another is
damaged or altered due to interference or degradation of the signal.
● Typographical Errors: Occur when a person makes a mistake while typing or writing,
such as mistyping a word or letter, leaving out a word, or using the wrong key.
● Transposition Errors: Occur when two digits are swapped or reversed in a number or a
piece of data, causing the data to become incorrect.
Data Verification versus Data Validation
There are two ways of preventing errors made by humans:
● Data verification refers to the process of checking if data from a source document is
entered correctly in the computer.
● Data validation refers to the process of checking data for accuracy and completeness
ensuring it is in the right format.
Methods of Data Verification
● Double Entry is a method of verifying data accuracy where data is entered twice, and
the two entries are compared to each other.
● Proofreading/Visual Checks refer to the process of visually inspecting data to detect and
correct errors.
Methods of Validating Data
● Range check - verify that data falls within a specified range of values. For example, if a
data field is expected to contain a number between 1 and 100
● Data type check - verify that data is of the correct type. For Example entering letters and
numbers for a name.
● Consistency check - compare data you have entered against other data you have
entered. For example ensuring the date of birth field matches the age field
● Reasonableness checks - verify that data makes sense. For example, ensuring that the
number of subjects taken in CSEC is not an unrealistic number such as 100 subjects.
● Presence checks - verify that required data is entered and not missing. For example, if a
data field is required, the field is not left blank.
● Length checks - verify that data meets specific length requirements. For example, if a
data field is expected to contain a specific number of characters.
Methods of file organization and access methods
● Sequential file ordering refers to the method of storing and retrieving data in a logical or
sorted order e.g in ascending order by a key field such as name etc. This type of file
organization allows all records to be viewed when the file is opened because it
minimizes the number of disk accesses required.
● Indexed Sequential file ordering refer to storing records in a sequential manner, but with
an index/key added for quick access to specific records.This is ideal for situations where
specific records need to be retrieved frequently and efficiently
● Serial file ordering refers to a type of sequential file ordering where data is stored and
retrieved one after the other as they are added, with each new piece of data being
added to the end of the file.
● Random file/Direct ordering refers to a method where data is stored in any order using a
key and can be directly accessed in any order, rather than having to be accessed in the
order in which it was stored. This allows for faster access times, but requires more
complex organization of the data within the file.
Application Areas for file organization
archiving, payroll file, real time systems
