Researchers at NASA wanted to determine the effects of space flight on a rat's daily consumption of water. The following data represent the water consumption (in milliliters per day) at lift-off minus 1, return plus 1, and 1 month after return for six rats sent to space on the Spacelab Sciences 1 flight.

(a) What is the response variable in this study? What is the treatment? How many levels does it have?
(b) Normal probability plots for each treatment indicate that the requirement of normality is satisfied. Verify that the requirement of equal population variances for each treatment is satisfied.
(c) Is there sufficient evidence that the water consumption is different for the three days at the a = 0.05 level of significance?
(d) If the null hypothesis from part (c) was rejected, use Tukey's test to determine which pairwise means differ using a familywise error rate of a = 0.05.

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Lift-Off Minus 1 Rat Return Return Plus 1 Plus 1 Month 18.5 32 30 17.5 2 18 34 28.0 31 39 4 28.5 29 44 31.0 48 54 22.5 25 32