# Homogeneity of variance and ANOVA

## Assess homogeneity of variance when comparing three independent groups on a continuous outcome

The assumption of homogeneity of variance is the second statistical assumption that needs to be tested for when comparing three or more independent groups on a continuous outcome with ANOVA. Homogeneity of variance is assessed using Levene's Test for Equality of Variances. In order to meet the assumption of homogeneity of variance, the

Homogeneity of variance essentially makes sure that the distributions of the outcomes in each independent group are comparable and/or equal. If independent groups are not similar in this regard, spurious findings can be yielded. ANOVA should not be conducted on continuous variables that violate the assumption of homogeneity of variance. ANOVA should only be conducted on continuous outcomes between groups that have "equivalent" or similar variances.

*p*-value for Levene's Test should above .05. If Levene's Test yields a*p*-value below .05, then the assumption of homogeneity of variance has been violated.Homogeneity of variance essentially makes sure that the distributions of the outcomes in each independent group are comparable and/or equal. If independent groups are not similar in this regard, spurious findings can be yielded. ANOVA should not be conducted on continuous variables that violate the assumption of homogeneity of variance. ANOVA should only be conducted on continuous outcomes between groups that have "equivalent" or similar variances.

### The steps for assessing the assumption of homogeneity of variance for ANOVA in SPSS

1. Click

2. Drag the cursor over the

3. Click on

4. Click on the continuous outcome variable to highlight it.

5. Click on the

6. Click on the "grouping" variable to highlight it.

7. Click on the arrow to move the "grouping" variable into the

8. Click on the

9. In the

10. Click

11. Click

**.**__A__nalyze2. Drag the cursor over the

**Co**drop-down menu.__m__pare Means3. Click on

**.**__O__ne-way ANOVA4. Click on the continuous outcome variable to highlight it.

5. Click on the

**arrow**to move the outcome variable into the**D**box.__e__pendent List:6. Click on the "grouping" variable to highlight it.

7. Click on the arrow to move the "grouping" variable into the

**box.**__F__actor:8. Click on the

**button.**__O__ptions9. In the

**Statistics**table, click the**box.**__H__omogeneity of variance test10. Click

**Continue**.11. Click

**OK**.### The steps for interpreting the SPSS output for homogeneity of variance with ANOVA

In the

If the

If the

**Test of Homogeneity of Variances**table, look under the**Sig.**column.If the

*p*-value is**MORE THAN .05**, then researchers have**met the assumption of homogeneity of variance and can conduct a one-way ANOVA.**If the

*p*-value is**LESS THAN .05**, then researchers have**violated the assumption of homogeneity of variance and will use a non-parametric Kruskal-Wallis test**to conduct the analysis.### Was the assumption of homogeneity of variance met for ANOVA?

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