Overview for Equivalence Test for a 2x2 Crossover Design

Use Equivalence Test for a 2x2 Crossover Design to compare treatment means for data that was collected in a 2x2 crossover study. This analysis can help you determine whether the effects of a test drug are equivalent to the effects of a reference drug.

When you use an equivalence test for a 2x2 crossover design, you must specify a range of values that are "close enough" to be considered equivalent to the mean of the reference drug. This equivalence interval, also called the zone of equivalence, is based on your knowledge of the product or process and should be determined before you perform the test. The analysis then determines whether you have enough evidence to claim that the difference (or ratio) between the population means is within the interval of equivalence.

For example, an analyst wants to determine whether a generic antacid (test drug) is as effective in reducing stomach acidity (pH) as a brand-name antacid (reference drug). Using a 2x2 crossover design, the analyst measures the gastric pH of participants who use the two antacids. The antacids will be considered equivalent if the pH of the generic antacid is within 10% of the pH of the brand-name antacid. Using an equivalence test for a 2x2 crossover design, the analyst evaluates whether the effects of the two antacids are equivalent.

You can also use the equivalence test for 2x2 crossover design to perform superiority tests and inferiority tests, to evaluate whether the mean of the test drug is greater than or less than the mean of the reference drug.