Question

Calculate the mean for the following frequency distribution:Marks
15-19
20-24
25-29
30-34
35-39
40-44
Frequency
6
5
9
12
6
2

Answer 1

Answer: Mean = 28.625

Solution:

Marks ____freq___xi____di___difi

15-19 ____6_____17____-10___-60

20-24 ___5_____22____-5___-25

25-29 ___9_____27_____0___0

30-34 ___12____32_____5___60

35-39 ___6_____37_____10___60

40-44___2_____42_____15___30

let mean a = 27

$\Sigma f_{i}= 6 + 5 + 9 + 12 + 6 + 2 \\ \\ = 40$
sum of
$\Sigma f_{i}d_{i}= - 60 - 25 + 0 + 60 + 60 + 30 \\ \\ = 90 - 25 \\ \\ = 65$

Formula: Assume mean method

$\bar x=a + \frac{\Sigma f_{i}d_{i}}{\Sigma f_{i}} \\ \\ = 27 + \frac{65}{40} \\ \\ = 27 + 1.625 \\ \\ \bar x= 28.625$
Hope it helps you

Answer 2

the answer is 28.582