Dr. Tabor wanted to investigate the relationship between sleep and levels of alertness during a class for American university students. She gave surveys to 150 college freshmen in her introduction to psychology course, asking them to report how many hours they slept each night during a two-week period. Dr. Tabor also had the participants rate their level of alertness on a scale of 1 to 10, with 10 being the most alert each day at the end of class. Dr. Tabor compared the average amount of sleep reported by each participant along with their average score on the alertness scale on a graph to examine the data. The resulting correlation coefficient for Dr. Tabor’s data was +0.89.