Question

In the following data item series, calculate the first quadrant (Q₁), third quadrant (Q₃) and median (M) :

Size	Frequency
11-15	7
16-20	10
21-25	13
26-30	26
31-35	35
36-40	22
41-45	11
46-50	5

Answer 1

Size	Frequency	cf
11-15	7	7
16-20	10	17
21-25	13	30
26-30	26	56
31-35	35	91
36-40	22	113
41-45	11	124
46-50	5	129

Q₁ Class = N/4 = 130 /4 = Size of 32.25^th item

The size class interval of 32.25^th item will lie in the class 25.5-30.5.

The size class interval of 96.75^th item will lie in the class 35.5 – 40.5.

The size class interval of 64.5^th item is in the cumulative frequency 91 and it will lie in the class 30.5-35.5.