We attempted to run everything in triplicate so 3 of the treatment groups are triplicated. 1 treatment group is duplicated, and 1 group is the control (single). The weights of fish are tanks averages. The largest difference is a total of 22 grams, the smallest is a difference of less than 1 between tanks. anova. levenes-test. If the sample sizes are unequal (generally if the largest sample is more than 50% bigger than the smallest), Box’s Test can be used to test for homogeneity of covariance matrices (see Box’s Test). This is an extension of Bartlett’s Test as described in Homogeneity of Variances. As mentioned there, caution should be exercised and many an independent samples t-test for comparing 2 groups or. a one-way ANOVA for comparing 3+ groups. Both tests require the homogeneity (of variances) assumption: the population variances of the dependent variable must be equal within all groups. However, you don't always need this assumption: 3. The violation of each assumption need a specific action/transformation with your data. 4. If Levene's test is significant at the .000 level, i.e the third assumption is not satisfied and your Each group is an independent random sample from a normal population. Analysis of variance is robust to departures from normality, although the data should be symmetric. The groups should come from populations with equal variances. To test this assumption, use Levene's homogeneity-of-variance test. Obtaining a One-Way analysis of variance Re: Levene's Test In SAS and SPSS. Without knowing the options used between the two, i.e. program code, it is difficult to point towards specific possibilities. The documentation shows that the SAS default in Proc Anova for HOVTEST=Levene defaults to using squared residuals (Type=Square). ts.sps. In general, if the populations can be assumed to be symmetric, or at least similar in shape (e.g., all negatively skewed), and if the largest variance is no more than four times the contrasts should be tested with the separate variance test to avoid the homogeneity of variance assumption. SPSS output gives both the classic test for the contrast as well as a Welch-type correction that does not assume equal variances (labeled as the separate variance test in SPSS output). There hasn’t been an easy way to test Welch-style con- haOAin.

how to test homogeneity of variance in spss