A psychology professor wants to examine the relation between amount of sleep and test performance. The professor asks the students to write down how long they had slept the night before the final exam. The results showed a correlation of -.70 between the amount of sleep students reported and their exam scores. Which of the following best describes the results of the study?

This statement is incorrect because a correlation of -.70 indicates a significant negative relationship between the variables. A correlation of zero would suggest no relationship at all, whereas the negative correlation shown here demonstrates a clear inverse association.

This choice is also incorrect as correlations can indeed be negative, which is what the -.70 value indicates. Negative correlations are a valid statistical outcome and suggest that as one variable increases, the other decreases.

This option misinterprets the correlation coefficient. While a correlation of -.70 indicates a strong relationship, to determine the percentage of variance accounted for, one would square the correlation coefficient. Squaring -.70 yields approximately 49%, not 70%, so this statement is inaccurate.