Comparing more means: ANOVA

Use Minitab to test if your numerical variable has the same true mean for the different levels of your 3+ level categorical variable.

a) Write down the null and alternative hypotheses to examine this question using ANOVA.

b) Assumption checking:             

(i) State the assumptions for the ANOVA test.

(ii) Use Mintab to check whether these assumptions are valid for your data. (Hint: use Normal Probability Plots, compare the sample standard deviations and comment on independence).

(iii) Discuss whether your data needs transforming. If a transformation is needed, select a suitable transformation and transform your data.

c) Use Minitab to carry out the ANOVA on your (transformed if necessary) data.

(i) State the test statistic and corresponding p-value.

(ii) Explain whether you have evidence for or against the null hypothesis.

(iii) State your conclusion in a form that a non-statistician would understand.