Going to college adds 15 pounds, right? Not according to this report. The story reports that a group of researchers interviewed over 7,000 people aged 17 to 20. The study found that freshmen in the sample gained, on average, 2.5 to 3.5 pounds in the past year. However, the study
also found that young adults who do not go to college gain weight — about a half pound less than college students of the same age. In other words, college attendance has almost no effect on weight gain.
a) What kind of study is this? An experiment, or a quasi-experiment?
b) What are the independent and dependent variables?
c) The story reports no difference in weight gain between college students and non-college students. This is a null effect. Do you think this null effect is attributable to some obscuring factors (such as those listed in Table 10.2)?
a) This is a quasi-experiment, because the main independent variable (being in college or not) was not manipulated by the experimenters. People can't be randomly assigned to attend college or not. This is an example of a non-equivalent control group design.
b) The study's independent variable was attending college or not, and the dependent variable was weight gain.
c) The potentially obscuring variables that are relevant to this study are situation noise (there are likely many situational differences within the various college and non-college environments) and individual differences. However, the study used so many people--over 7,000--and this most likely counteracted the large degree of within-groups variance. Therefore it might be safe to conclude that there truly is no difference in weight gain between college and non-college young adults.