Enter your data for Test for Equal Variances (Data tab)

On the Data tab of the Test for Equal Variances dialog box, specify the data for your analysis and enter a confidence level for the Bonferroni simultaneous confidence intervals.

Enter your data

Select the option that best describes your data.

Responses are in one column for all factor levels

Complete the following steps if your response data for all groups or factor levels are in one column.

  1. From the drop-down list, select Responses are in one column for all factor levels.
  2. In Response, enter the column that contains the numeric data.
  3. In Factors, enter one or more columns that contain the group classifications.
In this worksheet, Corrections is the response and contains the observed number of steering corrections for each driver. Experience and Road type are categorical factors that might relate to the variability in the number of steering corrections.
C1 C2 C3
Corrections Experience Road type
4 High First class
18 Low Second class
8 High Dirt
10 Low First class

Responses are in a separate column for each factor level

Complete the following steps if the response data for each group are in different columns. If you have one categorical factor, each column is a level of that factor. If you have more than one categorical factor, each column is a group that is a combination of factor levels from all factors.

  1. From the drop-down list, select Responses are in a separate column for each factor level.
  2. In Responses, enter at least two and no more than 12 columns of numeric data that you want to analyze.
In this worksheet, High_First, Low_First, High_Second, Low_Second and so on contain the correction times for a specific combination of experience level and road type. For example, the first column records the correction times for drivers who have high experience and drive on first class roads.
C1 C2 C3 C4 C5 C6
High_First Low_First High_Second Low_Second High_Dirt Low_Dirt
4 10 12 18 8 13
2 4 5 9 13 11
11 20 6 9 5 9
10 31 7 7 4 7

Confidence level

Enter a confidence level for the Bonferroni simultaneous confidence intervals. Usually, a simultaneous confidence level of 95% works well.

The simultaneous confidence level is the percentage of times that a set of confidence intervals includes the true standard deviations for all group comparisons, if you repeat the study multiple times. A 95% simultaneous confidence level indicates that, if you perform the study 100 times, the entire set of confidence intervals contains the population standard deviations for all groups in 95 of the studies.

For more information, go to Understanding individual and simultaneous confidence levels in multiple comparisons and What is the Bonferroni method?.

Use test and confidence intervals based on normal distribution

If you know that your data follow a normal distribution, select Use test and confidence intervals based on normal distribution to use Bartlett's test rather than the multiple comparisons test and Levene's test. If there are only 2 groups, the F-test is used instead of Bartlett's test.

The F-test and Bartlett's test are accurate only for normally distributed data. Any departure from normality can cause these tests to provide inaccurate results.

By using this site you agree to the use of cookies for analytics and personalized content.  Read our policy