Dr. Nicolas Guegen uses observational methods to study how certain kinds of environmental stimuli influence human behavior. In one study, he manipulated the volume of music played in bars to see how it would impact patrons' drinking behaviors. Trained observers recorded the minutes to drink, the number of drinks ordered, and the number of swallows to drink by several patrons in two establishments. The sound level was manipulated in both establishments, and all observations occurred over three Saturday nights. they used two sound levels in his study as determined by the noise level of the music playing: a normal sound level of 72 decibels (dB), which is similar to traffic noise on a busy street, and a louder high-volume level of 88 dB, which is similar to noise from a lawn mower. He reported significant differences in the minutes to drink and the number of drinks ordered, but not the number of swallows to drink. Sound level of environmental music and drinking behavior: a field experiment with beer drinkers.

Suppose you also are interested in how the noise level affects the patrons' drinking habits, but you also wonder how these effects might interact with the lighting level. You conduct a similar study except that you focus on whether there are differences in the average number of drinks ordered per person during the observation period for the two different noise conditions and two different lighting conditions (dark and normal). You randomly sample 24 bars in a large metropolitan area, and randomly assign each to one of the four sound and lighting conditions. Each of the 24 bars was observed for the same length of time on the same Saturday night.

The following table contains your hypothetical data:

Normal light 1.6 3.6 2.2 3.5 1.8 4.1 3.7 2.3 3.0 3.1 3.6 3.3

Dark light 4.6 4.1 4.0 3.8 2.6 3.0 3.6 4.3 3.4 4.6 2.4 3.6