7.59 Noise levels in fitness classes. Fitness classes often have very loud music that could affect hearing. One study collected noise levels (decibels) in both high-intensity and low-intensity fitness classes across eight commercial gyms in Sydney, Australia.29

  1. (a) Create a histogram or Normal quantile plot for the high-intensity classes. Do the same for the low-intensity classes. Are the distributions reasonably Normal? Summarize the distributions in words.

  2. (b) Test the equality of means using a two-sided alternative hypothesis and significance level .

  3. (c) Are the t procedures appropriate given your observations in part (a)? Explain your answer.

  4. (d) Remove the one low decibel reading for the low-intensity group and redo the significance test. How does this outlier affect the results?

  5. (e) Do you think the results of the significance test from part (b) or (d) should be reported? Explain your answer.