Of course, the real study is not encompassed by this question. The real study checked if the answer given was different if the prior proportion of lawyers was 30% with 70% engineers or 70% lawyers and 30% engineers. The estimates people gave did not vary based on prior probability.
Now that I think about this one, I think maybe the probability really is 30%. They don't say how they selected the lawyers and engineers. Maybe they selected patent lawyers (required to have engineering degrees) and all 70 members of the Society of Women Locomotive Engineers. Maybe they selected people at random. We don't know. Since we don't know the priors, we can't apply any reasoning about any characteristics of Jack.
In fact, they didn't say how they selected Jack either. Maybe they picked him out just to humiliate quiz takers who don't know the PI is a sadist.
This is a classic case of abusing the student by proving trick questions without essential information.
Now that I think about this one, I think maybe the probability really is 30%. They don't say how they selected the lawyers and engineers. Maybe they selected patent lawyers (required to have engineering degrees) and all 70 members of the Society of Women Locomotive Engineers. Maybe they selected people at random. We don't know. Since we don't know the priors, we can't apply any reasoning about any characteristics of Jack.
In fact, they didn't say how they selected Jack either. Maybe they picked him out just to humiliate quiz takers who don't know the PI is a sadist.
This is a classic case of abusing the student by proving trick questions without essential information.