Could be false. Maybe there were 1,000 original type A volunteers and 10 type B! Also, we don’t know if the type B volunteers’ heart disease risk reduced. Maybe a factor other than cholesterol or lipid type changed during the experiment and counteracted the cholesterol changes.

Could be false. While we know that type B volunteers’ cholesterol dropped in the experiment, we don’t know how high their cholesterol actually was. Nor do we know anything about the type A lipid profile people’s cholesterol, other than that it did not change in the experiment.

Could be false. We have no idea what other behaviors volunteers engaged in during the experiment! That’s a reason why we can’t draw valid inferences about the actual impact of low-fat diets from the stimulus—we can only draw inferences about the results of this one experiment.

Must be false. The only volunteers who experienced a reduction in cholesterol levels (the original type B people) did not experience a change in their lipid profiles.

Must be true. People with a type B lipid profile are at greater risk of heart disease, so when 40% of the original type A volunteers experienced a shift to type B profiles and no benefits to counteract that change, they ended up at higher risk for heart disease.