## Wednesday, August 26, 2009

### How to investigate importance of Variance with F -test

F- Test is important tool for investigating the importance of variance with F - Test . We can explain it with simple example

Suppose , There is the sample of 8 Variables , and total of Variance from mean is 94.5 . Another sample of 10 variables total of variance from mean is 101.7 . Investigate whether its variance are important or not ?

Solution :

Ho : Q1 's power two = Q2 's power two
n1 = 8
Sigma ( X1 - mean 1 ) power 2 = 94.5
n2 = 10

Sigma ( X2 - mean 2 ) power 2 = 101.7

S1's power 2 = 94.5/8-1 = 13.5 ; S2's power 2 = 101.7 / 10-1 = 11.3

F = S1power 2/S2's power 2 = 13.5 / 11.5 = 1.195

Decision :
F's calculated value is less than F's table value , so variance is not so important . Our assumption is true .
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