Top Law Schools

I put down choice (A) as the correct choice. This statement, if valid, would show that while there is an 18 percent reported incidence rate, it is not due to the increased virulence of the virus.

Why is this reasoning wrong?

Why is choice (D) the correct answer?

Thank you!

That's a tricky wrong answer! I think it's crucial to not pick the first nice answer that walks along and instead assume you've been fooled and look for a better one.

Here, the argument is concluding that the disease has become stronger. Why? Because a great percent of cattle who contract it now die, as compared to 5 years ago.

Since this is a weaken question, we're looking for any assumptions. The large one -- which is probably too large to show up in an answer choice -- is "Could the rise in the mortality rate be because of some other reason?" So what could be a specific reason? For one, there could be some physical explanation; for instance, perhaps the cattle that the disease is now affecting are weaker than the original ones who contracted the disease (perhaps it started in Texas Long Horn and then moved to some flimsy breed raised in New Hampshire?). The other area for alternate explanations that should come to mind is that the numbers might be somehow wrong. Whenever the LSAT brings up percents, be on the look-out for whether the totals have been somehow tampered with. This takes different forms (which is too large a discussion for here). In this case, one way to disrupt the argument is to suggest that the number of cattle that now gets the disease is actually larger than we think, then that 18% who now die would actually be lower.

To put some numbers behind this:

2005: 100 cows contract disease and 5 die. 5% mortality.
2010: 500 cows contract disease, BUT we only know about 100, and 20 die. 4% mortality, but it looks like it's 18%!

(D) takes advantage of this possible number play.

(A) is incorrect because it has the opposite effect of (D) -- it raises the number of cattle that were recently killed by the disease, which strengthens the conclusion that the disease has become more virulent.
(B) suggests the disease was not as strong as originally thought, perhaps strengthening the conclusion.
(C) is irrelevant. What does the inoculation program have to do with whether the disease and whether it's become stronger?
(E) is similarly irrelevant. It does not weaken the idea that the disease has become stronger.

Does that make sense? If so, you might want to try and figure out a different answer choice that would have done the same sort of weakness but focused on the original mortality rate.

A typical LSAT percentage trick
Whenever i see the proportions involved i expect to see some kind of play with numbers, which is why i get them right.
Be critical of these types of questions.

Awesomeness! Thank you for your reply!

Another question for you:

Preptest 17 December 1995 Section 2 Question 10

The correct choice is (A). Why? The answer reads that the apples have been washed. Regardless where it is washed, as long as it is washed, it is clean.

I picked choice (B).

Could you explain why (A) is correct?

Here you go, my colleague explained this one a while back: http://www.atlaslsat.com/forums/pt-17-s ... -t256.html