Professor Izadi is interested in determining the association between sleep and cognitive performance. He surveyed his students about the number of hours they slept the night before an exam and then correlated these scores with their test grades. He found a .81 correlation between these two variables. What does this result mean?

There is a high positive correlation between sleep and exam performance

Explanation:

Correlation studies the degree of association between two variables. A correlation coefficient of 0.5 to 1 is regarded as a strong correlation, that is an increase in one variable will result in an increase in the other variable. A correlation coefficient that lies between 0.3 to 0.49 is regarded as moderately correlated while a value of 0 means that there is no correlation.

Thus, the result of this study shows that an increase in sleeping time will result in better exam performance.