The information which is collected by the investigator himself with a definite objective in his mind is called as primary data
when the information is gathered from a source which already had the information stored, it is called as secondary data.
It can be observed that the data in 1, 3, and 5 is secondary data and the data in 2 and 4 is primary data.
The blood groups of 30 students of Class VIII are recoded as follows:
A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O,
A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O.
Represent this data in the form of a frequency distribution table. Which is the most common, and which is the rarest, blood group among these students?
The frequency means the number of students having same blood group.
It can be observed that 9 students have their blood group as A,
6 as B,
3 as AB, and
12 as O.
Therefore, the blood group of 30 students of the class can be represented as follows.
Blood group 
Number of students 
A 
9 
B 
6 
AB 
3 
O 
12 
Total 
30 
It can be observed clearly that
Most common Blood Group (Highest frequency): O (maximum number of students)
Rarest Blood Group (Lowest frequency): AB  (minimum number of students)
The distance (in km) of 40 engineers from their residence to their place of work were found as follows:
5 3 10 20 25 11 13 7 12 31
19 10 12 17 18 11 32 17 16 2
7 9 7 8 3 5 12 15 18 3
12 14 2 9 6 15 15 7 6 12
Construct a grouped frequency distribution table with class size 5 for the data given above taking the first interval as 0  5 (5 not included). What main feature do you observe from this tabular representation?
It is given that a grouped frequency distribution table of class size 5 has to be constructed. Therefore, the class intervals will be 0  5, 5  10, 10  15, 15  20…
By observing the data given as above, a grouped frequency distribution table can be constructed as follows.
Distance (in km) 
Tally mark 
Number of engineers 
0  5 
5 

5  10 

11 
10  15 

11 
15  20 

9 
20  25 
1 

25  30 
1 

30  35 

2 
Total 
40 
It can be observed that there are very few engineers whose homes are at more than or equal to 20 km distance from their work place. Most of the engineers have their workplace up to 15 km distance from their homes.
The relative humidity (in %) of a certain city for a month of 30 days was as follows:
98.1 98.6 99.2 90.3 86.5 95.3 92.9 96.3 94.2 95.1
89.2 92.3 97.1 93.5 92.7 95.1 97.2 93.3 95.2 97.3
96.2 92.1 84.9 90.2 95.7 98.3 97.3 96.1 92.1 89
(i) Construct a grouped frequency distribution table with classes
84  86, 86  88
(ii) Which month or season do you think this data is about?
(iii) What is the range of this data?
(i) A grouped frequency distribution table of class size 2 has to be constructed. The class intervals will be 84  86, 86  88, and 88  90…
By observing the data given above, the required table can be constructed as follows.
Relative humidity (in %) 
Number of days (frequency ) 
84  86 
1 
86  88 
1 
88  90 
2 
90  92 
2 
92  94 
7 
94  96 
6 
96  98 
7 
98  100 
4 
Total 
30 
(ii) It can be observed that the relative humidity is high. Therefore, the data is about a month of rainy season.
(iii) Range of data = Maximum value  Minimum value
= 99.2  84.9 = 14.3