In Exercise 8.32 on page 512 we consider an ANOVA to test for difference in mean gill beat rates for fish in water with three different levels of calcium. The data are stored in FishGills3. If the ANOVA table indicates that the mean gill rates differ due to the calcium levels, determine which levels lead to different means. If the ANOVA shows no significant difference, find a confidence interval for the mean gill rate at each level of calcium.

Exercise 8.32

Most fish use gills for respiration in water and researchers can observe how fast a fish’s gill cover beats to study ventilation, much like we might observe breathing rate for a person. Professor Brad Baldwin is interested in how water chemistry might affect gill beat rates. In one experiment he randomly assigned fish to tanks with different levels of calcium. One tank was low in calcium (0.71 mg/L), the second tank had a medium amount (5.24 mg/L), and the third tank had water with a high calcium level (18.24 mg/L). His research team counted gill rates (beats per minute) for samples of 30 fish in each tank. The results are stored in FishGills3. (Note: You may also see a file called FishGills12 which is a more extensive experiment with 12 tanks.)