Question

Construct the grouped frequency table from the following:

Class marks	15	25	35	45	55	65
Frequencу	7	12	18	22	16	5

Answer 1

Given: Class marks: 15, 25, 35, 45, 55, 65 with corresponding frequencies 7, 12, 18, 22, 16, 5.

Step-wise calculation:

1. Class-size = Difference between consecutive class marks

= 25 – 15

= 10

2. Half class-size = `10/2`   ...(Used to get class limits from class marks)

= 5 

3. Construct class-intervals by subtracting/adding half class size to each class mark:

For class-mark 15: interval = 15 – 5 to 15 + 5 → 10 – 20

For 25: 20 – 30

For 35: 30 – 40

For 45: 40 – 50

For 55: 50 – 60

For 65: 60 – 70

4. Assign the given frequencies to these intervals in the same order.

Class interval	Frequency
10 – 20	7
20 – 30	12
30 – 40	18
40 – 50	22
50 – 60	16
60 – 70	5
Total	80