Gue? guen and jacob (2012) asked female restaurant wait staff to wear different colored t-shirts on different days for a six-week period and recorded the tips left by male customers. the results show that male customers gave significantly bigger tips when the wait persons were wearing red. what is the independent variable for this study? number of male customers who left a tip size of tip day on which the wait person wore red color of the t-shirt (red versus not red) what is the dependent variable for this study? number of male customers who left a tip size of tip color of the t-shirt (red versus not red) day on which the wait person wore red what scale of measurement is used for the independent variable? ordinal interval ratio nominal