| The F Test
is used to compare the variances of two
samples to test the hypothesis
that the samples are drawn from
populations with different variances:
H0 the samples are drawn from
populations with equal variances
H1 the samples are drawn from
populations with different variances
The F test is based on the ratio of the
variances of the two samples:
| |
1 |
2 |
3 |
4 |
5 |
Variance |
|
Sample A |
8.7 |
9.8 |
12.2 |
12.9 |
9.5 |
3.327 |
|
Sample B |
23.8 |
21.5 |
18.3 |
24.3 |
22.9 |
5.788 |
This gives an F statistic:
(Most tables give critical
values greater than 1, so divide the larger
by the smaller)
This can be compared to the critical F
value from tables, or the p-value
can be obtained using the Excel function:
=FDIST(Fo, DOFn,
DOFd) = 0.302
DOFn and DOFd are the Degrees
of Freedom of the numerator and denominator
(both are 4 in this example)
The F Test is based on the
F
Distribution.
|
