Perhaps the mice with light at night in Exercise 8.24 are gaining more weight because they are eating more. Computer output is shown for average food consumption (in grams) during week 4 of the study for each of the three light conditions.

(a) Is it appropriate to conduct an ANOVA test with these data? Why or why not?
(b) A randomization test is conducted using these data and the randomization distribution is shown in Figure 8.7. The randomization test gives a p-value of 0.652. Clearly state the conclusion of the test in the context of this data situation.

Figure 8.7

Studies have shown that exposure to light at night is harmful to human health. Data A.1 on page 136 introduces a study in mice showing that even low-level light at night can interfere with normal eating and sleeping cycles and can have an effect on weight gain and glucose intolerance. In the study, mice were randomly assigned to live in one of three light conditions: LD had a standard light/dark cycle, LL had bright light all the time, and DM had dim light when there normally would have been darkness.

Data A.1 on page 136

Numerous studies have shown that exposure to light at night is harmful to human health. A recent study in mice shows that even low-level light at night can interfere with normal eating and sleeping cycles. Furthermore, the study finds that food is especially fattening if consumed at the wrong time of day, at least in mice. In the study, 27 mice were randomly split into three groups. One group was on a normal light€“dark cycle (LD), one group had bright light on all the time (LL), and one group had light during the day and dim light at night (DM). The dim light was equivalent to having a television set on in a room. The mice in darkness ate most of their food during their active (nighttime) period, matching the behavior of mice in the wild. The mice in both dim light and bright light, however, consumed more than half of their food during the well-lit rest period, when most mice are sleeping. Although the data collected show that the three groups of mice ate approximately the same amount of food and had the same levels of physical activity, the mice exposed to light at night gained substantially more weight, ate a greater percent of calories during the day, and were more likely to be classified as glucose intolerant at the end of the study. An absence of darkness seems to be associated with fatter mice.

Transcribed Image Text:

Level Mean 4.1241 StDev 0.6938 0.4337 1.3149 DM 10 4.3275 4.5149 LD LL 2 4-