Numerous studies have demonstrated a pronounced negative correlation between high–fiber diets and the incidence of co...

shunhe on June 13, 2020

Hi @kenken,

Thanks for the question! So let’s take a look at the stimulus. We’re told that studies have shown a negative correlation between high-fiber diets and incidence of colon cancer. In other words, more fiber in the diet, less colon cancer; less fiber in the diet, more colon cancer. We’re given some examples, and then the argument concludes that basically, an insufficient consumption of fiber causes colon cancer, and sufficient consumption of fiber prevents it.

Now we’re asked for a weakness in the argument, and something should’ve caught your eye when you read this. You should pay attention when the LSAT uses terms like “causes,” because there is a big difference between causation and correlation. The author basically assumed from these correlations causation, which can be a big no-no. For example, ice cream sales and swimming pool deaths both go up in the summer, but neither of these causes the other. They’re both influenced by a third variable. So one weakness that you can anticipate is going to be something along those lines, and this is what (E) tells us. If foods containing fiber just have other things that do the actual work of preventing colon cancer, then the fiber itself isn’t doing any work, it just happens to be there usually when the colon cancer preventers are there. This is a possibility the argument overlooks, and so (E) is the correct answer.

Hope this helps! Feel free to ask any other questions that you might have.