Question

Chapter 8, Section 1, Exercise 033

LIGHT AT NIGHT MAKES FAT MICE
Studies have shown that exposure to light at night is harmful to human health. A study in mice shows that light at night has an effect on weight gain after just three weeks. 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.

when calories are consumed

Researchers hypothesized that the increased weight gain seen in mice with light at night might be caused by when the mice are eating. Perhaps mice with light at night eat a greater percentage of their food during the day, when they normally should be sleeping. Conditions for ANOVA are met and computer output for the percentage of food consumed during the day for each of the three light conditions is shown.

Level   N   Mean   Stdev

DM     10   22.516 10.881
LD      8     36.028    8.403
LL       9     76.573    9.646

One-Way ANOVA: Corticosterone versus light

Source    DF / SS /        MS/       F/     P
Light       2 /      6987.0/ 3493.5/   36.39/ 0.000
Error       24/   2304.3/      96.0
Total       26/     9291.2

Note: (/ are used to separate in the table since the text keeps jumping weird spaces)

(a) For mice in this sample on a standard light/dark cycle, what is the average percent of food consumed during the day? What percent is consumed at night? What about mice that had dim light at night?

Round your answers to one decimal place.

Standard Cycle: Day ________%
                           Night________ %
Dim light: Day__________ %
              Night___________%

(b) Is there evidence that light at night influences when food is consumed by mice?

Yes or No

c) Can we conclude that there is a cause-and-effect relationship?

Yes or No

Answer 1

(a):

Standard Cycle: Day 36.0%
                           Night 36.0%
Dim light: Day 22.5%
              Night 22.5%

(b): Yes, there evidence that light at night influences when food is consumed by mice.

See in anova table the p value is 0.00 that is less than 0.05, there is significant effect of light in food.

(c): cause-and-effect relationship means when one event create other events.

Yes, there is a cause-and-effect relationship because light is one event and create other event weight gain.