1.

Find the mean of each of the following frequency distributions: Class interval: 0 - 10 10 - 12 20 - 30  30 - 40 40 - 50 Frequency: 9 12 15 10 14

Answer»

Let the assumed mean (A) = 25

 class interval Mid value (xi)  di = xi - 25 ui = \(\frac{xi-25}{10}\) Frequency (fi) fiui
 0 - 105-20-29-18
 10 - 2015-10-112-12
 20 - 302500150
 30 - 40351011010
 40 - 50452021428
 N = 60\(\sum\)fiui = 8

We have, 

A = 25

h = 10

Mean = A + h x \(\frac{\sum f_iu_i}{N}\)

\(=25+10\times\frac{8}{60}\)

\(=25+\frac{8}{6}\)

\(=25+\frac{4}{3}=26.333\)


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