Julie finds that the number of hours she sleeps each night is related to the scores she receives on quizzes the next day. as her sleep approaches 8 hours, her quiz scores improve; as her sleep drops to 5 hours, her quiz scores show a similar decline. julie realizes that there is a correlation between her hours of sleep and her grades.

"six months ago, several of molly's friends joined the trimtime fitness center. each of them participated in trimtime's weight-reduction and fitness regimen. all reported substantial weight reduction, and all are visibly slimmer. molly is convinced. she joins trimtime and enrolls in the program, hoping and expecting to see the same results. she is especially delighted to learn that trimtime had adjusted its program to make it even more effective in a shorter period of time." what is the feature in question/attribute of interest in this argument?