3. Observing differences between between-treatments variance and within-treatments variance Dr. Nicholas 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 number of swallows taken to finish a drink by several patrons in two establishments. The sound level was manipulated in both establishments, and all observations occurred over three Saturday nights. Dr. Guegen used two sound levels in his study: a normal sound level of 72 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. You decide to replicate this study. The null hypothesis is that there is no difference between the mean number of swallows taken to finish a drink among patrons experiencing the high- volume noise level of 88 dB and the mean number of swallows taken to finish a drink among those experiencing the normal noise level of 72 dB. The alternative hypothesis is that there is a difference between the mean number of swallows taken to finish a drink among patrons experiencing the louder noise level of 88 dB and the mean number of swallows taken to finish a drink among those experiencing the normal noise level of 72 dB. Below are the graphs of two possible data sets. The horizontal axes display the number of swallows taken to finish a drink, while the vertical axes display the number of observed patrons who took that number of swallows to finish a drink. Use these graphs to answer the questions that follow. a Patrons Observed High Volume (33 db) 10 11 12 13 14 15 Number of Swallows to Finish Hormal (72 dhi Patrons Observed High Volume (88 db) 357 11 12 15 Number of Swallows to Finish