Question

Find the mean of each of the following frequency distributions:
Class interval:
0-6
6-12
12-18
18-24
24-30
Frequency:
6
8
10
9
7

Answer 1

STEP DEVIATION METHOD:

Step deviation method is used in the cases where the deviation from the assumed mean 'A' are multiples of a common number. If the values of ‘di’ for each class is a multiple of ‘h’ the calculation become simpler by taking ui= di/h = (xi - A )/h

Here, h is the class size of each class interval.

★★ Find the class marks of class interval. These class marks would serve as the representative of whole class and are represented by xi.  

★★ Class marks (xi)  = ( lower limit + upper limit) /2

★★ We may take Assumed mean 'A’ to be that xi which lies in the middle of x1 ,x2 …..xn

MEAN = A + h ×(Σfiui /Σfi) , where ui =  (xi - A )/h

FREQUENCY DISTRIBUTION TABLE IS IN THE ATTACHMENT  

From the table : Σfiui = 3  , Σfi = 40

Let the assumed mean, A = 15,  h = 6

MEAN = A + h ×(Σfiui /Σfi)

MEAN = 15  + 6 (3/40)

= 15 + 18/40

= 15 + 9/20

= 15 + 0.45

Mean = 15.45

Hence, the mean is 15.45

HOPE THIS ANSWER WILL HELP YOU….

Answer 2

hope it helps



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answer is 15.45