PrepTest 127

Incorrect. This answer concludes that a day was pleasant, so we should look to Principle #1. To reach that conclusion, it would need to be shown that there was intermittent wind and the temperature stayed below 84F. Since there was no wind, it fails to establish the first sufficient condition, so this answer is unsupported.

Incorrect. This answer concludes that a day was oppressive, so we should look to Principle #2. To reach that conclusion, it would need to be shown that there was high humidity, and either the temperature stayed above 84F or there was no wind. Since humidity levels weren't high, however, this answer is incorrect.

Incorrect. This answer concludes that a day was pleasant, so we should look to Principle #1. To reach that conclusion, it would need to be shown that there was intermittent wind and the temperature stayed below 84F. However, the temperature stayed at 84F all day, so that sufficient condition isn't met (and this is the trap answer we anticipated!).

Incorrect. This answer concludes that a day was oppressive, so we should look to Principle #2. To reach that conclusion, it would need to be shown that there was high humidity, and either the temperature stayed above 84F or there was no wind. It does establish that humidity levels were high, but there was both wind and temperatures below 84F all day, so it doesn't meet the either/or part of the sufficient condition and is thus unsupported.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True (Principle)

Stimulus Summary:
(1) Intermittent wind AND Temp below 84F → Pleasant summer day
(2) High humidity AND (Temp above 84F OR not Wind) → Oppressive summer day

Answer Anticipation:
Must Be True (Principle) questions generally present two conditionals that allow related judgments to be drawn. Our process is to diagram these statements out, get the related judgments in the necessary conditions, and then find an answer that reaches one of those judgments after meeting the sufficient condition(s).

Before we get into the details of our diagram, we can note that the conditionals present sufficient conditions for a summer day to be either pleasant or oppressive, so the related judgments are already in the necessary condition. We won't need to take contrapositives here, and we know what conclusions we can justify (pleasant; oppressive).

Now, let's get into our diagram.

The first principle is relatively straightforward. It has an AND in there, and the sufficient condition starts halfway through the statement, but If is an easier conditional indicator word. With all that noted, we end up with the conditional diagram you see in our summary.

The second principle is much more complicated, and it'd be very easy to miss that "High humidity" term. We'll circle back to talk about what to do if you missed it after walking through our diagram. However, the "either if" tells us that the second half of this sentence is an OR sufficient condition, which matches with the parenthetical. We know that High humidity is a sufficient condition because the rule only applies if the summer day has high humidity. It doesn't make sense to say that it's a necessary condition—necessary for what? If you put it in the necessary condition, that would mean that a day with a high temperature or no wind is humid, and that's simply not the case. With that noted, we can see that the second principle applies on days when there's high humidity AND one of the two options that it presents. That's also why we threw the OR in parentheses—to note that that's a distinct sufficient condition added onto high humidity.

One more note before we circle back to if you missed the humidity term—note the temperatures from the stimulus. Principle #1 talks about temperatures below 84F, and Principle #2 talks about temperatures above 84F. Neither addresses temperatures at 84F, so we should expect a trap answer about that temperature.

Now, what to do if you had missed the High humidity condition and just had the OR sufficient condition? It wouldn't have been a problem! As long as you're considering all answer choices—and you are, right?—and if the correct answer relied on Principle #2 and there were two that used the incorrect shortened version correctly, you would have ended up with multiple answers that looked correct. You would have compared them and seen the relevant difference was that one answer noted there was high humidity. Then, you would have checked the stimulus and seen that high humidity was relevant to that principle, and you would have (slightly more slowly) still answered this question correctly.

Answer Explanation:
This answer concludes that a day was oppressive, so we should look to Principle #2. To reach that conclusion, it would need to be shown that there was high humidity, and either the temperature stayed above 84F or there was no wind. Humidity was high, and there was no wind, which is sufficient to guarantee the conclusion regardless of temperatures. This answer is therefore supported by the second principle.

Key Takeaway:
More difficult Must Be True (Principle) questions will throw more complex conditionals your way. Take the diagramming portion of your work slowly to make sure you have everything correct—doing so will make it very efficient to work through the questions!