Minitab includes several equivalence tests to help you evaluate whether a population mean is equivalent to a target value or to the mean of another population.
1-sample equivalence test
Compare the mean of a product or a process to a standard. In Minitab, choose Stat > Equivalence Tests > 1-Sample.
For example, an engineer experiments with a new way to seal potato chip bags. The engineer wants to ensure that the force required to open the bags is within 10% of the target value of 4.2 N (Newtons). The engineer collects 28 bags that are sealed using the new method and tests the force required to open them.
2-sample equivalence test
Compare two product means or two process means using two independent samples. In Minitab, choose Stat > Equivalence Tests > 2-Sample.
For example, a pet food company creates a new, less expensive formulation of their popular cat food for discount retailers. Analysts want to ensure that the protein content of the discount food is the same as that of their original food. The analysts measure the amount of protein per 100 grams of food in both formulations and test whether they are equivalent within ± 0.5 grams.
Equivalence test with paired data
Compare two product means or two process means when observations are paired, such as when measurements for two treatments are taken from the same person or part. In Minitab, choose Stat > Equivalence Tests > Paired.
For example, an eyewear company develops a new cleaning solution for contact lenses. Analysts want to verify that the new solution cleans lenses as well as the leading brand. Analysts have 14 participants wear contact lenses for a day, and then clean the lenses. Each participant cleans one lens in the new solution and the other lens in the leading brand. By using paired observations, the analysts reduce the amount of variability that is caused by differences between participants. Finally, the analysts assess the cleanliness of each lens by measuring the angle of contact for a drop of fluid on the lens. The angle of contact is affected by film or deposits on the lens.
Equivalence test for a 2x2 crossover design
Compare treatment means for data from a 2x2 crossover study. 2x2 crossover studies are commonly used to test whether individual participants experience equivalent effects on two different drugs. In Minitab, choose Stat > Equivalence Tests > 2x2
Crossover Design.
For example, analysts at a pharmaceutical company want to determine whether their generic antacid is equivalent to a name-brand antacid. Two groups of participants receive 5-days of one antacid, followed by a 2-week washout period, and then 5-days of the other antacid. The analysts measure gastric pH on the last day of each treatment. Because lower pH values are more acidic, higher values mean the drug is more effective. The analysts will consider the antacids equivalent if the test pH is within 10% of the reference pH.
