A group of 268 overweight people signed up for a weight loss program. Participants were asked to choose whether they wanted to go on a vegetarian diet or follow a traditional low-calorie diet that included some meat. 153 people chose the vegetarian diet, and the rest chose to be in the control group and continue to eat meat. There was a greater weight loss in the vegetarian group.
a. What is the sample size of each group? What percentage of people was in the vegetarian group? What percentage was in the meat group? (Round to the nearest percent.)
b. What are the variables in this study? Remember that variables are used to record characteristics of individual people or things. The description above does not necessarily name all the variables – you have to make an educated guess about what characteristics were measured and recorded in order to conduct this study. For each variable, indicate whether it is a categorical variable or a numerical variable, and explain why.
c. What confounding variables might account for the increased weight loss in the vegetarian group? Explain.
d. Is this an observational or a controlled study?
e. Describe a better way to design the study that is more likely to remove the effect of confounding variables. Make sure to use the ideas covered in section 1.4 of your text.
