Organisation of Data — Economics STD 11 Commerce — Question

To understand these terms we are taking two series for reference one is discrete frequency distribution and second is continuous frequency distribution. Series-1 Discrete Frequency Distribution

Shoe Size	7	8	9	10	11	12
No of students	8	12	20	10	6	4

Series 2 Continuous Frequency Distribution

Marks	0-10	10-20	20-30	30-40	40-50	50-60
No of students	8	12	20	10	6	4

1. Frequency: Frequency is the number of times a value repeats itself in the observations. For example when we have written 8 before 7 in series 1, it means 8 students have a shoe size of 7 number in raw data. 12 students have got 8 size, 20 got 9 size and so on. It is applicable to discrete frequency distribution
2. Class Frequency: Frequency of a class instead of specific observation is called class frequency. It shows how many items have a value in that class interval. For example, when we have written 10 in column of number of students in front of 30-40, it means 10 students have got marks equal to or more than 30 but less than 40.
3. Class: It refers to decided group of magnitudes. For example, 0-10 in series 2. It may be 0-9, 10-19 or 4.5 – 8.5 and so on.
4. Upper and Lower limits of the Class: Lower limit is the lower magnitude of the class and upper limit is the upper magnitude of class. For example in class 0-10, 10 is the lower limit and 10 is the upper limit.
5. Total Frequency: It is the sum total of frequencies of all classes. It must be equal to total number of observations.
6. Frequency Distribution: When observations are distributed over several values, it is termed as frequency distribution. For example, in above examples, I series is an example of discrete frequency distribution of shoe El size of students. Series 2 is a continuous 2 frequency distribution of marks obtained TREI by students.
7. Class Interval: Class Interval refers to the magnitude spread between the lower and upper class limit. In other words, it is span or width of the class. It can be obtained by deducting lower limit from upper limit. It is applicable to continuous series only. In series two, class interval is 10 (10-0=10) for first class and for other classes as well. But it is not necessary that all classes should have same class interval. Depending on the purpose, unequal class intervals for different classes can also be used. For example:

Pocket Expenses Frequency	Frequency
0-10	2
10-30	9
30-100	3
100-500	5
500-1000	4
1000-2000	2

8. Mid Value: It is the average of lower limit and upper limit. It can be obtained by dividing the sum of lower limit and upper limit by 2. For example, in series 2 given above, we can find mid values as follows:

Daily Income	No of families	Mid Value
0-100	5	50
100-200	9	150
200-300	12	250
300-400	2	350
500-600	2	450

1. Discrete Series: A series which See represents a discrete variable is called discrete series. For example, series -1 of shoe size is a discrete series.
2. Continuous Series: A series which represents continuous variable is called a continuous series. For example, in series 2, the distribution of marks amongst students is a continuous series.