Testing the difference between two variances- Sept. 7, 2012

According to what I've learned...

Characteristics of F-distribution

-The values of F cannot be negative
-The distribution is positively skewed
-The mean value of F is approximately equal to 1
-The F distribution is a family of curves bases on the degrees of freedom of the variance of the numerator and the degree of freedom of the denominator.

Formula for F-test

Use of F-test
1. The larger the variance should always be designated as variance sub 1 and be placed in the numerator formula.
2. For a two tailed test, the alpha must be divided and the critical value be placed on the right side of the f curve.
3. If the standard deviations instead of the variances are given in the problem, they must be squared for the formula for the F-test.
4. When the degrees of freedom cannot be found in table H. the closest value on the smaller side should be used.

Assumptions for testing difference between two variances
1. The populations from which the samples were obtained must be normally distributed.
2. The samples must be independent of each other.

That's all...
By: Carl Joel E. Palma III-Gold