Professor Hartwick finds that people who tend to score low on one variable tend to score low on another variable. Professor Hartwick has found: a. a correlation coefficient that is less than zero. b. a negative correlation. c. a positive correlation. d. no relationship.

Option C) a positive correlation.

Step-by-step explanation:

We are given the following in the question:

" People who tend to score low on one variable tend to score low on another variable."

Correlation:

Correlation is a technique that help us to find or define a linear relationship between two variables. It is a measure of linear relationship between two quantities. A positive correlation means that an increase in one quantity leads to an increase in another quantity  or decrease in one quantity leads to decrease in another quantity.A negative correlation means with increase in one quantity the other quantity decreases. +1 tells about a a perfect positive linear relationship and −1 indicates a perfect negative linear relationship.

Since, for the given case with decrease in one variable other also decreases, thus, it is an example of positive correlation. Thus, the correlation coefficient cannot be less than or equal to zero.

Thus, the correct answer is

Option C) a positive correlation.