The F-test is a test for a difference in dispersion (variance) between two independent samples.
The requirements of the test are:
Data in existing Excel worksheets can be used and should be arranged in a List dataset layout or Table dataset layout. The dataset must contain a continuous scale variable and a nominal/ordinal scale variable containing two independent groups.
When entering new data we recommend using New Dataset to create a new 2 variables (1 categorical) dataset ready for data entry.
To start the test:
Excel 97, 2000, 2002 & 2003:
Select any cell in the range containing the dataset to analyse, then click Analyse on the Analyse-it toolbar, click Compare Groups then click F test.
If your dataset is arranged using the list layoutClick Variable and select the dependent variable, then click Factor and select the independent variable containing the two groups to compare.
The report shows the number of observations analysed, and, if applicable, how many missing values were excluded. Summary statistics for each sample are then shown.
The ratio of the variances and confidence interval are shown. A ratio of variances near 1 indicates the variances are similar.
The F statistic and hypothesis test are shown. The p-value is the probability of rejecting the null hypothesis, that the samples have the same variance, when it is in fact true. A significant p-value implies that the two samples have different variances.