Real Life Logic: The (Il-)logic Of Test Prep Advertising

It always makes me laugh when I see LSAT prep companies make a big deal out of how well their instructors scored on the test, and it always baffled me how people could possibly take that as an indication of how good the instruction is. But I think I may have figured it out.

We can start with an utterly uncontroversial statement – just because you can do something doesn’t mean you can teach someone else how to do it. I’m pretty sure that no matter who you ask, you’d get agreement to that statement. And yet, over and over again, commercial test prep companies use that as a line to “prove” how good their instruction is, and I always wondered – how could anyone, anywhere EVER fall for that, given even fifteen seconds to think it over? Well, I think I figured it out, and it’s actually kind of funny because it’s an LSAT concept. Are you ready? Here it is:

The people who fall for these lines are confusing a necessary condition with a sufficient condition.

Examining the thought process of these folks really does clear up a lot. What do you think when you hear that someone scored 170+ on the LSAT? Probably the first thing that goes through your head is some variant of “that’s a really good score, that guy must know what he’s doing.” At the very least you’re sure that he knows his stuff – whether he can teach it to you effectively is a separate question. Conversely, if you hear about some guy who scored 140 on his LSAT, you probably wouldn’t trust him or her to teach you how to do it. Why? Because he’s demonstrated, via his test score, that he doesn’t know what’s going on, so how on earth could he ever teach you anything? Thinking about it in these terms, the relationship is:

Teach LSAT Well -> Scored Well

If someone teaches the LSAT well, that implies that they scored well, which makes sense – after all, you yourself have to know what’s going on before you can teach it to others. And, if someone didn’t score well, that implies that they can’t teach well – because how can you ever teach a subject if you yourself don’t know what’s going on? In other words, the people who use the statement about scoring well as some kind of proxy for teaching ability are actually just committing a fundamental logical error – they are affirming a necessary condition and concluding the sufficient condition must be true. This teacher scored better than this other guy on the LSAT, so he MUST be able to teach it better too…right? That conclusion goes right in the toilet when you see firsthand (as I have) that some 180 scorers have no clue how to teach others how to do the same, while people who never even sniffed that score turn out to be far superior instructors. Of course, there’s a threshold past which this no longer holds true – people who score poorly still wind up being exceedingly poor teachers, for reasons that I hope are fairly intuitive.

To be clear – test prep companies have to put statements like this out there. The fact that scoring well is a necessary condition for teaching well means that they still have to give that information to you, or else there’s no chance that you’d ever take a course from them. You’d just walk away asking “why should I trust these yahoos?” It’s not a coincidence, though, that test prep companies artificially inflate the importance of this claim and push it as a differentiating factor – they do it because it works on a LOT of people. Sufficient/necessary confusion still works on a ton of people who have LSAT/formal logic instruction – can you even imagine how well it works on people who don’t?

This is funny specifically in the context of the LSAT because hey, if you fall for that line and sign up for, say, Testmasters based on that claim (their instructors are all required to have scored in the 99th percentile, and that’s a major selling point for them), week 1 of classes should immediately make you regret it – assuming, of course, you understand what’s being put in front of you.

So it ends up being like this – the people who are the worst at logic are the same people who are most likely to sign up for a commercial LSAT course (which is essentially a bad commercial course in logic), due to their poor logical reasoning skills. Or, in other words, these people make bad LSAT prep choices specifically because they’re bad at the skills the LSAT tests.

What a world.

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