Exercise 13.2.5
It is hard to disagree with the purposes of this study reducing the prevalence of obesity. But does it really show what it claims? Be a deliberate skeptic for a moment and ask yourself these questions:
Exercise 13.2.6
If the students were volunteers, how typical do you think they are of all students?
Exercise 13.2.7
And if the teachers are receiving a large research grant to implement the program, might they be working harder to do a good job than most of us ordinarily work?
Exercise 13.2.8
An important ambiguity about the program was the fact that it included both physical activity and homework assistance. Think about this ambiguity.
Exercise 13.2.9
If the researchers split up these two elements offering only one or the other at any one school how might the split affect the outcomes?
Exercise 13.2.10
Would different sorts of students volunteer as a result of the split, and how if at all would their selection matter?
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