Question

3) The use of the Bonferroni adjustment is said to be a “conservative” approach for making multiple comparisons among unstructured treatment means. Which statement about this adjustment is correct?

a) The comparisonwise error rate is set to a high level based on the number of comparisons that are being made.

b) The experimentwise error rate is effectively controlled at the specified alpha level.

c) The Type II error rate is low.

d) The power to detect differences is very high.

Answer 1

Bonferroni correction is a conservative test that, although protects from Type I Error, is vulnerable to Type II errors (failing to reject the null hypothesis when you should in fact reject the null hypothesis). Thus, Type II error rate is high and power to detect differences can be low.

The comparison - wise error rate is the probability of a Type I error set by the experimenter for evaluating each comparison.  The comparisonwise error rate is set to a reasonable level

The experiment - wise error rate is the probability of making at least one Type I error when performing the whole set of comparisons. The experimentwise error rate is alpha level divided by the  number of comparisons that are being made.

b) The experimentwise error rate is effectively controlled at the specified alpha level.