Imagine that you are conducting an observational study to see if getting less sleep correlates with more or less happiness during the day. You use a group of 10 close friends
as subjects for the study. You design a Web-based application that allows volunteers to
track the amount of sleep they get each night and to rate their happiness three times during
the day. Your friends are interested in your study and want to see it succeed, so they are
willing to answer all survey questions when they are supposed to answer them. You find a
strong positive correlation between the hours of sleep and self-reported happiness.

1.)Name one example of bias that might be at work. Explain how this hidden variable
could affect the results.

2.)Does the study prove that getting more hours of sleep will make people happier? What principle of science proves your answer, and what is one reason why this principle is true?

3.)Imagine a scatter plot of the data from this study, showing hours of sleep across the bottom (0,-10) and happiness scores on the right (0,-10).

Draw and label two scatter plots, one that shows a weak positive correlation and one that shows a strong positive correlation. Use 10 data points in each of your plots.