Logical reasoning PrepTest 152 · Section 2 · Question 9

Incorrect. This answer eliminates a potential source of bias, suggesting fairness if anything.

Incorrect. The rules being published ahead of time doesn't let us know that the rules as applied were fair or not. That said, again, the rules being published ahead of time, if anything, removes a source of shenanigans.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
Fair lottery → Every entrant has equal chancesBut 90% of winners entered in the first 2 days of the 30-day period, so the lottery wasn't fair.

Answer Anticipation:
Be careful with this conditional rule! It's not a guarantee that a lottery will be fair, but rather a rule of what a lottery must do to be fair. Since the argument is meant to conclude that the lottery broke these rules and thus wasn't fair, it's important to understand this correctly. That's why we wrote it the way we did—go back over it to make sure you understand what it's saying.

Since the conclusion is that the lottery wasn't fair, let's take the contrapositive of our conditional:

not Every entrant has equal chances → not Lottery fair

Does the premise presented establish that everyone didn't have equal chances? It's trying to do so by suggesting the lottery was skewed towards people who entered early, but it doesn't directly state that. So is there something that could explain how 90% of winners entered in the first 2 days of the 30 day period (other than random chance, which the LSAT tends to shy away from presenting as an answer)? Sure—if 90% of entrants entered in the first 2 days! If that's the case, and everyone did have equal chances, then it'd be expected that 90% of people entered early. Since we're trying to strengthen the argument that this lottery was not fair, we want an answer that says this didn't happen.

Answer Explanation:
This answer eliminates the possibility that the vast majority of entrants entered in the first 2 days, thus explaining why so many winners were selected from that group. If the entrants entered evenly throughout the period, the 90% of winners coming from the first 2 days looks fishy, strengthening the conclusion.

Key Takeaway:
First, be careful with conditionals—make sure that you understand what it means while rotely applying the rules. Here, it would have been easy to end up with a conditional stating Lottery → Fair, which would be incorrect.

Second, when an argument you know is flawed (as all arguments in certain question types, including Strengthen, must be) applies a conditional in a seemingly straightforward way, there's a good chance that there's a term shift in the premise that establishes the sufficient condition. It's a great place to look for a flaw.

Incorrect. Again, if anything, posting the rules in a highly visible place ("conspicuously") would suggest fairness.

Incorrect. The number of entrants doesn't speak to fairness, equal chances of winning, or when people entered compared to when the winners entered.