The objective of commercials is to have as many as viewers as possible remember the product in a favourable way and eventually buy it. In an experiment to determine how the length of a commercial affects people's memory of it, 50 randomly selected people were asked to watch a half-hour TV show. In the middle of it, a commercial advertising of a brand-new product appeared. Each viewer was exposed to varying lengths of the commercial, ranging between 20 to 60 seconds, but its essential content was the same. After the TV show finished, each person took a test to determine how much he/she remember about the product. The commercial times (CT) and test scores (TS) (on a 30-point test) are recorded.

A simple regression model of the form: TS_i = b₀ + b₁CT_i + e_i, i=1,...,52, was estimated with the least squares method and an excerpt from the output is shown partially as follows: