Abstract: The present Monte Carlo study compared Type I error rates of four tests under nonnormality and
heterogeneity of variance asslimptions. Cochran test, Brown -Forsythe test, modified Brown -Forsythe test and
approximate ANOVA F test were evaluated for three -and six different groups. At the end of 50,00 simulation
trials, the Type I error rates for four tests were affected by the sample size, variance ratio, the number of groups
and die relationship between sample sizes and groups variances. Type I error rates of the Brown Forsythe test,
extension of the modified Brown -Forsythe test and approximate ANOVA F-test were close to the predetermined
alpha levels (0.05), while Cochran tests greatly deviated from the predetermined level.