Question

New research \(^{62}\) supports the idea that people who get a good night's sleep look more attractive. In the study, 23 subjects ages 18 to 31 were photographed twice, once after a good night's sleep and once after being kept awake for 31 hours. Hair, make-up, clothing, and lighting were the same for both photographs. Observers then rated the photographs for attractiveness, and the average rating under the two conditions was compared. The researchers report in the British Medical Journal that "Our findings show that sleep- deprived people appear less attractive compared with when they are well rested." (a) What is the explanatory variable? What is the response variable? (b) Is this an experiment or an observational study? If it is an experiment, is it a randomized comparative design or a matched pairs design? (c) Can we conclude that sleep deprivation causes people to look less attractive? Why or why not?

Short answer

The explanatory variable is the sleep-status (sleep-deprived or well-rested) and the response variable is the attractiveness rating. The study is an experiment and the design is matched pairs. Further, the study suggests that sleep-deprivation can make people look less attractive. However, one should consider other potential factors.

Step-by-step solution

Identify the Variables

The explanatory variable is sleep-deprivation or a good night's sleep. It is the independent variable that is manipulated. The response variable, or the dependent variable, is attractiveness. This is what is being measured in response to the changes in the explanatory variable.

Classify the Study Type

This study is an experiment, not an observational study, because the researchers actively manipulated a variable. That's why the subjects were deliberately kept awake for a period of 31 hours while a comparative group was rested.

Determine the Design Type

The study design is a matched pairs design. This is because each subject was treated under both conditions: good night's sleep and sleep-deprivation. The same subjects were used for direct comparison, hence this is a matched pairs design as opposed to a completely randomized design.

Evaluate Cause-Effect Relationship

The experiment suggests that sleep-deprivation causes people to look less attractive. This statement comes from the controlled setup where other factors such as hair, make-up, clothing, and lighting were kept constant which allows us to focus on the impact of sleep only. However, caution should be taken as there might be other unknown variables that could have affected the outcome i.e. individual's health, mood etc.