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What are the assumptions of ANCOVA?
Posted May 19, 2022
Answer
Your data must meet the following assumptions for a one-way ANCOVA to give you a valid result:
- The dependent variable and covariate variables are measured on a continuous scale (at the interval or ratio level).
- The independent variable consists of two or more categorical, independent groups.
- There is independence of observations (there is no relationship between the observations in each group or between the groups themselves).
- There are no significant outliers or no points within data that do not follow the regular pattern.
- The dependent variable is approximately normally distributed within each subpopulation.
- There is homogeneity of variances (the variance of the dependent variable is equal over all subpopulations).
- The covariate is linearly related to the dependent variable at each level of the independent variable.
- There is homogeneity of regression slopes (there is no interaction between the independent variable and the covariate).