a weight-loss app that combines dietary and exercise advice wanted to market itself to men wanting to lose weight. researchers for the app recruited 27 healthy overweight men into a 2-month study. they randomly assigned 9 men to use the app, 9 men to follow a popular diet, and 9 men to increase their normal exercise level. the men were weighed at the beginning and the end of the study, and the amount of weight loss was calculated for each man. what is the factor in this study?