Journalist: A recent study showed

Answer choices

1. A

   Unclear Impact16% picked this

   whether people who exercise regularly are more likely to drink decaffeinated beverages than those

   This answer is tempting, because it's potentially identifying a Third Factor. Exercising regularly is correlated with decaf, so could it be that exercising regularly is really what's causing the higher rates of arthritis? This is definitely worth keeping on a first pass, but is there a good common sense connection between "regular exercise" and "developing arthritis"? Does regular exercise damage connective tissue? It really depends on the exercise, which is why ultimately it's unclear what impact this has. Running or playing basketball on hard surfaces is probably damaging to joints, but swimming or yoga presumably is not (and may even strengthen connective tissue).

   16%
2. B

   Irrelevant Comparison4% picked this

   whether people who drink decaffeinated coffee tend to drink coffee less often than those who

   The study controlled for how much coffee was consumed by the participants. Both the decaf drinkers and the regular drinkers were consuming 3 cups per day. So we can't devise an alternate explanation for these study results that involves different amounts of consumption.

   4%
3. C

   Correct72% picked this

   whether the degeneration of connective tissue is slowed by consumption of caffeine

   Why this is right

   This presents an Alternate Explanation for why the decaf drinkers were twice as likely as the regular coffee drinker to develop arthritis: it's not (as the author is concluding) that decaf contains something bad that increases your likelihood of getting arthritis, it's that regular coffee contains something good (caffeine, which is not in decaf) that decreases your likelihood of getting arthritis. This is a tricky alternate explanation, because the coffee is still the causal reason for the difference in arthritis risk, but saying that "caffeinated coffee has an ingredient that helps to discourage arthritis" is a different explanation than "decaf coffee has an ingredient that helps to encourage arthritis. If you want to try a similar problem with that sort of trick, try this one.

   Skill tested: Evaluate · how this choice captures the argument's function is the move to repeat next time.

   72%
4. D

   Irrelevant1% picked this

   whether most coffee drinkers drink more than three cups of coffee

   It doesn't matter whether at least 51% of coffee drinkers drink more than 3 cups a day, or whether it's only 49% at most that drink more than 3 cups a day. Neither one of those has any effect on us judging whether or not decaf has an ingredient that damages connective tissue.

   1%
5. E

   Irrelevant Comparison6% picked this

   whether people who have arthritis are less likely than the general population to drink coffee

   The study controlled for how much coffee was consumed by the participants. Both the decaf drinkers and the regular drinkers were consuming 3 cups per day. So this answer can't possibly offer us an alternate explanation for the study results. If an answer said, "Whether people who have arthritis are advised by their doctors to avoid decaf coffee" that would be somewhat relevant, because it would increase the plausibility that there is something chemically dangerous about decaf when it comes to arthritis.

   6%