Exercises
- Investigate the effect of skewness on the type I error rate by running simulations
with at least 8 different parameter settings. Show your results in a table
and write a summary statement of the effect of skewness.
- Investigate the effect of homogeneity of variance on the type I error rate
by running simulations with at least 8 different parameter settings. In all
cases, make the sample sizes for the two groups equal. Show your results in
a table and write a summary statement of the effect of homogeneity of variance.
- Repeat question 2 except this time make the sample sizes different. Show
your results in a table and write a summary statement. When does violating
the assumption of homogeneity of variance lead to an inflated type I error
rate? When does it lead to a type I error rate that is below the stated level?
- Compare the power of a design with sample sizes of 5 and 15 with the power of a design with sample sizes of 10 and 10.
- Describe the effects of the sample size and the standard deviation on the type I error rate and on power?