If the winner of a promotional contest is selected by a lottery, the lottery must be fair, giving all entrants an equ...

Mehran on November 13, 2018

Hi @elfume, thanks for your post. Let's first examine the stimulus. This one presents an argument. The conclusion is "it is clear that this lottery did not meet the fairness test." Why? What are the premises provided in support of this conclusion? The first premise is a principle (a general rule with at least one sufficient and one necessary condition): if the winner of a promotional contest is selected by a lottery, the lottery must be fair, giving all entrants an equal chance of winning. The second premise tells us that 90% of the winners selected by the lottery in a recent promotional contest submitted their entry forms within the first 2 days of the 30-day registration period. From this fact, the conclusion is drawn.

The problem is that this is not a strong argument. What if 90% of the people who entered this contest did so within the first 2 days? Then the fact that 90% of the winners came from the pool of people who entered in the first 2 days of the registration period is *not* an indication that this lottery was unfair, right?

The question stem asks us to STRENGTHEN this argument - in other words, we have to strengthen the conclusion that this lottery was unfair. Answer choice (C) does this. If people entered the contest at a consistent rate throughout the 30-day registration period, then it would indeed be unfair if 90% of the winners came from just the first 2 days of this registration period. This is because the vast majority of the entrants would have come from the latter 28 days of the registration period, yet these entrants would have been mostly overlooked for selection (only 10% of the winners would have come from the last 28 days of the registration period; this is unfair).

Hope this helps! Please let us know if you have any additional questions.