Page 3 - Lesson note -1 -Ch.14 Statistics( Introduction,Presentation of Data)

Secondary data: The data collected by someone, other than the investigator, are
known as secondary data.
Secondary data should be carefully used, since they are collected with a purpose
different from that of the investigator and may not be fully relevant to the investigation.

Question2: Why do we arrange the data?
Solution: The data which is obtained in original form is called raw data. It is difficult to
get information from the raw data and is rather confusing sometime. Data is arranged so
that it becomes understandable and can be interpreted. Rearrangement of data is
helpful to make calculations of certain values which will help in describing and analyzing
the data.
Question 3: Explain the meaning of the following terms:
(i) Variate
(ii) Class-interval
(iii) Class-size
(iv) Class-mark
(v)Range
(vi) Frequency
(vii) Class limits
(viii)True class limits
Solution:
(i) Variate: Any character that can vary from one individual to another.
(ii) Class- interval (Group): In the data of each group into which raw data is
considered.
(iii) Class-size: The difference between the upper limit and lower limit of a grouped
data is called class size.
(iv) Class-mark: The middle value of the selected class interval or group is called Class
Mark.
It can be calculated as: Class-mark = (Upper limit + Lower limit)
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(v)Range: The difference between the highest and lowest observation is called Range
of data.
(vi) Frequency: The number of times a particular observation occurs in a data or
corresponding to class interval or group.
(vii) Class limits: Each class is bounded by two figures, called the class limits. The
figure on the right side are called upper limit while figure on the left side of the class
are called lower limit.
(viii)True class limits: If classes are inclusive (Discontinuous). For example: 5-9, 10-14,
15-19 and so on
Then, true lower limit of class = Lower limit of class - 0.5
And, true upper limit of class = Upper limit of class + 0.5
In this case, True limits of the class is 5-9 are 4.5 and 9.5
But if classes are exclusive(continuous) like 20-30, 30-40, 40-50 and so on, then class
limits and true class limits are the same.

Question 4: The ages of ten students of a group are given below. The ages have
been recorded in Years and months: