ABSTRACT
In broad terms, an experiment is a scientific activity in which procedures and conditions are controlled as carefully as possible so as to isolate the effect of some kind of deliberate manipulation. The key word is “controlled”—to perform an experiment, the scientist must have control over the conditions that might affect the results. Most studies are concerned with detecting differences in central tendency among groups, and the methods discussed in this chapter will largely be concerned with that problem. That is, methods for testing hypotheses about whether certain populations differ in terms of some variable on the average are considered. Central tendency does not tell the whole story. Some studies are more concerned with detecting differences in variability among groups. The sizes of parts produced by two manufacturing processes are compared, one of which is substantially less costly.
