Question

Find out the standard deviation of the following by step deviation method-
Marks No. Of students
20-40 6
40-60 9
60-80 8
80-100 10
100-120 11
120-140 6​

Answer 1

Answer:

X Mid point (X) Frequency (F) i=class interval width A=50

Σf=40 Σfu=40

The formula used for arithmetic mean of grouped data by step deviation method is,

X =A+ ∑fu/∑f ×i

A= Assumed mean of the given data

∑ = Summation of the frequencies given in the grouped data

∑fu = Summation of the frequencies and deviation of a given mean data

u= (x−A)/i

i= Class interval width

X = arithmetic mean

X =50+ 40/40 ×20

=50+20

=70

Explanation:

Hope so it helps