4 - Hypothesis testing

Summary

Introduction

Often, a researcher, engineer, or clinician will formulate a statement or a belief about a certain method, treatment, or behavior with respect to one or more populations of people, animals, or objects. For example, a bioengineer might be interested in determining if a new batch of drug-coated stents has a drug coat thickness that is different from a previous batch of stents. The engineer makes several measurements on a small number of stents chosen at random. A substantial deviation in drug coating thickness from the standard range of acceptable values indicates that the process conditions have unexpectedly changed. The stents from the new batch may have either a thicker or a thinner drug coating compared to those of the previous batches, depending on the direction of deviation in coat thickness. Or, it is possible that the drug coat thickness widely fluctuates in the new batches of stents beyond the range specified by design criteria. The engineer formulates a hypothesis based on her preliminary survey. She will need to perform statistical tests to confirm her hypothesis.

Suppose a biomaterials researcher is testing a group of new promising materials that enhance the durability or lifetime of a contact lens. The researcher poses a number of hypotheses regarding the performance qualities of different lens materials. She must use statistical techniques to test her hypotheses and draw appropriate conclusions.