The article claims that watching TV is causing kindergartners to gain weight. The evidence is that the kindergartners who watch TV each day weigh more than the kindergartners who don’t watch TV each day. The problem in this study is that it omitted a third variable. When you are watching TV, you usually do it sitting and often for a prolong period of time, so the kindergartners who are watching TV are not engaged in a physical activity as often. The third variable could simply be that the kindergartners who watch TV every day are not as active as those who don’t watch TV every day. The fact that they are not as active could be causing them to gain weight not the TV
