The data referenced in this project is LightatNight8weeks. If you are unable to answer all questions, I will post another set separately. Please Help (Stat Key is also good to use for this assignment) I attached an excel spreadsheet for this project as well (LightatNight8weeks.csv)

 

In Data 4.1 on page 000, we examine a study in which mice were randomly assigned to either a normal light/dark cycle or to have a light on around the clock. According to the paper describing that study, “The global increase in the prevalence of obesity and metabolic disorders coincides with the increase of exposure to light at night.” The study is examining whether light at night plays a causal role in the obesity epidemic. In Data 4.1, we examine the effect of the different light conditions on body mass gain after three weeks. In fact, the actual experiment lasted 8 weeks and examined many additional variables.1 The data referenced here are available in LightatNight8weeks. Some of the variables are summarized in the following table.

1. What are the cases? What is the explanatory variable? Is this a randomized experiment or an observational study?

2. What is the mean body mass gain for all the mice in this dataset? What is the five number summary? Show a graph of the body mass gains in the sample. Do there appear to be any outliers? Find and interpret a 95% confidence interval for mean body mass gain.

3. The primary question in the study was whether having a light on at night causes greater average body mass gain. Give side-by side boxplots comparing body mass gain for the two groups. Does having a light on at night appear to increase body mass gain in mice?

4. Conduct a hypothesis test to see if the data provide evidence that mean body mass gain is higher for mice with a light on at night. Show all details of the test. If the results are significant, can we conclude that there is a causal association? Why or why not?

5. To examine how large is the effect on body mass gain of having a light on at night, give a 99% confidence interval for the difference in mean body mass gain between mice with a light on at night and mice with darkness at night. Interpret the interval in context.

6. Perhaps the difference in weight gain between the two groups was affected by a difference in food consumption. Conduct a hypothesis test for a difference in mean consumption between the two groups. Is there evidence of a significant difference in average food consumption between the two groups?

7. Perhaps the difference in weight gain between the two groups was affected by a difference in activity level. Conduct a hypothesis test for a difference in mean activity level between the two groups. Is there evidence of a significant difference in average activity level between the two groups?

tNight8weeks.csV d LightatNight8weeks.csv (4 Bytes) Condition BMGain Light Dark Light Light Dark Corticoster DayPct Consumptic Glucoselnt GTT15 3.387 Yes GTT120 Activity 328.704 134.483 9.89 42.132 71.552 378.704 5752 5.02 87.838 31.063 61.453 3.791 No 228.448 1437 1256 148.238 92.191 191.22 51.999 67.7 41.017 12.252 21.817 9.58 11.2 6.67 3.451 No 3.501 Yes 379.091 366.129 231.183 392.373 226.563 323.077 466.346 500 259.615 348.78 85.978 41.408 64.827 227.273 383.871 220.43 250 244 3.923 No 4.24 No 4.489 No 4.161 No 3.479 Yes 4.416 No 2541 1231 346 5837 3582 877 Light Dark Dark 9.05 8.17 2.79 12.33 8.13 9.39 10.88 6.34 9.37 6.32 17.4 3.97 47.573 34.947 141.406 199.038 470.192 190.361 413.462 126.016 118.333 286.957 153.719 405.941 230 Light Dark 81.6 41.94 87 257 70.441 40.5 84.415 28.95 81.636 21.846 5.94 Yes 4.586 No 2657 153 Light Light Dark Light Dark Light Dark 3 132.4 23.403 8.615 70.47 66.679 56.718 1649 4482 728 6702 4.89 No 280 4.873 Yes 4.946 No 7.177 Yes 4.004 No 335.652 299.174 435.644 461.25 6048