Not necessary, because to be a proving ground, the intention is that the classes will prevent people who are NOT the most committed from receiving passing grades. But that doesn’t mean the classes are designed to guarantee that those who ARE the most committed will receive passing grades.

Not necessary, because whether science departments need to have “proving grounds” classes is not relevant to whether certain classes are in fact acting as “proving grounds.” We care about whether the classes are successful “proving grounds,” not about whether these classes are necessary for science departments.

Not necessary, because to be a proving ground, the intention is that the classes will prevent people who are NOT the most committed from receiving passing grades. But whether anyone is IS the most committed gets passing grade doesn’t affect whether the class is a proving ground.

Necessary, because if it were not true — if SOME of the students in the intro courses who are least enthusiastic about science ARE among the most committed to being science majors — then the fact some of the least enthusiastic students get passing grades wouldn’t establish that the “proving grounds” purpose isn’t successful. The least enthusiastic students who get passing grades MIGHT be among the most committed to being science majors; if that’s the case, we have no reason to think the intro classes aren’t weeding out students who are not the most committed to being science majors.

Not necessary, because whether intro courses “should” be proving grounds is irrelevant. What matters is whether they are successfully acting as proving grounds, not whether they should have that purpose.