Lucinda will soon be attending National University as an engineering major. At National University, most residents of...

shunhe on December 28, 2019

Hi @Julie-V,

This is a match the flaw question, so first, let's figure out what the flaw in the stimulus is. We know that Lucinda is an engineering major, and at the university she's attending, most residents of WH are engineering majors. From that, we conclude that she'll probably live in Western Hall. If you prefer diagrams, one informal way to diagram this is the following:

WH residents - Most - > Engineering majors

Engineering Major

Conclusion: Lucinda likely lives in WH.

We can see the problem here is that while we could say that if she lived in WH, she'd likely be an engineering major, we can't say the reverse. Imagine, for example, WH has 3 people in total, and 2 are engineering majors. Then most residents of WH are engineering majors. But if there are 100 engineering majors total on campus, then it's pretty unlikely (1/50 chance) Lucinda lives in WH. We need an answer stem with a similar reversal.

(A) does not parallel this flaw. A shopping mall is being constructed in the city, and most cities with shopping malls are regional economic hubs, so our city will probably become a regional economic hub. For those who prefer diagrams:

City with shopping mall - Most - > Regional economic hub

City with shopping mall

Conclusion: Likely regional economic hub

Which we can see does not parallel the flaw. In fact, there is not even a flaw in answer (A); it is perfectly valid inference. Hope this helps!