Question

1. Find missing frequency from the following data
Class Frequency
0 - 5 1
5 - 10 7
10 - 15 11
15 - 20 ?
20 - 25 ?
25 - 30 4
30 - 35 2
Total Frequency (N) = 40 and mean = 16.5

Answer 1

Let a and b be the missing frequencies of class intervals 5 – 10 and 20 – 25 respectively.

Then, 55 + a + b = 70⇒a +b=15 …..(1)

Median is 16, which lies in 15 – 20. So, the median class is 15 – 20.

∴ l = 15, h = 5, N = 70, f = 15 and cf = 24 + a

Now,

Median,

M=l+(N2−cff)×h

⇒16=15+(702−(24+a)15)×5

⇒16=15+(35−24−a3)

⇒16=15+(11−a3)

⇒16–15=11−a3

⇒ 1 × 3 = 11 – a

⇒ a = 11 – 3

⇒ a = 8

∴ b = 15 – a [From (1)]

⇒ b = 15 – 8

⇒ b = 7

Hence, a = 8 and b = 7.

Answer 2

Answer:

"refer the attached file "