# Correlation and Regression

December 12, 2016

Question
The text tells us that a Pearson correlation coefficient is a measure of the strength and direction of a linear relationship between two variables. A scatter plot provides a visual representation of the relationship. Answer the questions below, but use your own examples and do not take examples from the text.

Make up an example of two variables that might be related in such a way that the Pearson correlation coefficient could not be used to measure the relationship strength but the Spearman coefficient could be used instead. Explain the rationale for your answer.
Use an example to describe a situation where a scatter plot of the data would result in all of the data points falling exactly on a straight line. What would be the calculated value of r?
Use an example to describe a situation where a researcher might be misled into thinking there is a causal relationship between two variables when in fact there is none. Give three possible alternative explanations for the relationship.