In: Statistics and Probability
A study explored the effect of ethanol on sleep time. Fifteen rats were randomized to one of three treatments. Treatment 1 was water (control). Treatment 2 was 1g of ethanol per kg of body weight, and Treatment 3 was 2g/kg. The amount of REM sleep (in minutes) in a 24hr period was recorded:
Treatment 1 | 63 | 54 | 69 | 50 | 72 | |
Treatment 2 | 45 | 60 | 40 | 56 | ||
Treatment 3 | 31 | 40 | 45 | 25 | 23 | 28 |
Are these data strong evidence REM sleep time differs across the three treatment populations?
(a) Graph the data. Why did you choose the graph that you did and what does it tell you?
(b) Create an ANOVA table for the data using your calculator (to prepare for exams). Show your work. You may use R to check your answers.
(c) Evaluate the ANOVA assumptions graphically. Was ANOVA appropriate here?
(d) Based on the ANOVA table, make a conclusion in the context of the problem.
(e) Use R to create 95% CIs for all pairwise comparisons of means using the Tukey-Kramer method. Summarize your results using letter codes. What do you conclude?