EXAMPLE 5 Conserving energy

Many utility companies have introduced programs to encourage energy conservation among their customers. An electric company considers placing electronic meters in households to show what the cost would be if the electricity use at that moment continued for a month. Will meters reduce electricity use? Would cheaper methods work almost as well? The company decides to design an experiment.

One cheaper approach is to give customers an app and information about using the app to monitor their electricity use. The experiment compares these two approaches (meter, app) and also a control. The control group of customers receives information about energy conservation but no help in monitoring electricity use. The response variable is total electricity used in a year. The company finds 60 single-family residences in the same city willing to participate, so it assigns 20 residences at random to each of the three treatments. Figure 5.3 outlines the design.

To carry out the random assignment, label the 60 households 1 to 60; then use software to select an SRS of 20 to receive the meters. From those not selected, use software to select the 20 to receive the app. The remaining 20 form the control group. Lacking software, label the 60 households 01 to 60. Enter Table A to select an SRS of 20 to receive the meters. Continue in Table A, selecting 20 more to receive the app. The remaining 20 form the control group.