Researchers attempt to measure or control the influence of any variables other than the independent variable that could affect the dependent variable; these are control variables. If a research team wants to test the impact of package design on sales, they will need to control for other factors that can affect sales, including price and level of advertising, for example. Any variables that might affect the outcome of the experiment and which are not measured or controlled are called extraneous variables. Extraneous variables include the respondent’s mood or feelings, the temperature of the room in which the experiment is taking place, or even the general weather conditions at the time of the experiment. After the experiment, the researcher measures the dependent variable to see if it has changed. If it has, the researcher concludes that the change in the dependent variable is caused by the independent variable. The material in Exhibit 5.6 explains these concepts in more detail.