The function LeveneTest performs Levene's test for equal group variances. The data to be analysed must be stored in the array Data, the integer array TmLevel contains the corresponding group numbers (level of treatment). On return the function delivers the pvalue of the ANOVA and the corresponding F value in the variable parameter FStat. An error is indicated by a negative p value:
1 ... no groups defined
2 ... too many groups defined
3 ... F value is undefined (MS_{bw} and MS_{wi} are both zero)
4 ... Data and TmLevel arrays have different lengths
