Research papers in medical journals often cite variables that are correlated with one another.

a. Using a health-related example, indicate what investigators mean when they say that variables are correlated.

b. Give examples of variables in the medical field that are likely to be correlated.

Can you give examples of variables that are positively correlated and variables that are negatively correlated?

c. What are some examples of medical variables that are not correlated?

Provide a rationale for the lack of correlation among these variables.

d. Give an example of two variables that are strongly related but have a correlation of zero (as measured by a Pearson correlation coefficient).