1.

Find the mean of each of the following frequency distributions: Class interval: 25 - 35 35 - 45 45 - 55 55 - 65 65 - 75 Frequency: 6 10 8 12 4

Answer»

Let the assumed mean (A) = 50

 Class interval Mid value di = xi - 50 ui = \(\frac{X_i-50}{10}\) Frequency (fi) fiui
 25 - 35 30-20-26-12
 35 - 45 40-10-110-10
 45 - 55 500080
 55 - 65 601011212
 65 - 75 70202048
 N = 40\(\sum\)fiui = -2

We have, 

A = 50

h = 10

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

\(=50+10\times\frac{-2}{40}\)

\(=50-0.5\)

\(=49.5\)


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