Rock Fries Your Brains

David C. Howell

A high school student named David Merrell did a fascinating study of the effects of listening to rock music on the performance of rats in a maze. He had three groups of rats, one raised in the presence of rock music (performed by the group Anthrax), one raised in the presence of music by Mozart, and one raised in the absence of music. These animals learned to navigate a maze before exposure to the music, and then performed over three additional weeks.

The data for this study is found in anASCII file named Anthrax.txt. (Be careful of the ascii file because subject# 11 died in Week3 and data have been input with 999 as a missing value. You will have to tell your software about this or change to some other value.) The variables in the file are, in order, Subject, Group [1 = Control, 2=Mozart, 3=Anthrax], wk1r1, wk1r2, wk1r3, wk2r1 ... wkk4r3 [4 weeks of 3 runs each], week1 week2 week3 week4 [weekly means], wt1, wt2, wt3, wt4 [weekly weights], median1--median4 [weekly medians].

• Read the data into an available statistical analysis program.
• Calculate the descriptive statistics for Week1 -- Week4 and Wt1 -- Wt4.
• What conclusions would these data suggest?
• What would you expect the histograms for week 1 data and for week3 data to look like?
• Draw a histogram of the data for wk1r1 and for wk4r3.
• Draw a histogram for the data from week1 and week4.
• How do the histograms for the individual runs compare with the histograms for the weekly means?
• Now draw a histogram of median1 and median4.
• How does the distribution of medians compare with the other distributions?
• How would we decide whether to use means, medians, or raw scores in our analysis?
• Use the Boxplot procedure to compare the distributions among the three groups at each time period.

Last modified 3/6/2009