There are four types of assumption questions on the LSAT; today's tasks asks you to specify an obvious possibility given the stimulus' evidence. By negating that possibility, the answer choice will link up the evidence and its bridge or conclusion, closing up the "gap" that Zen students look for while attacking assumptions. The other assumption tasks include finding a missing direct logic link, definition and definition shift.
The answer in fails to consider assumption task will almost always be a negation of a possibility that could result in a different conclusion than the one drawn in the stimulus. Many test-prep companies describe this type of assumption question as a "necessary" assumption, in that it is required for the conclusion to stand but does not cover all possibilities problems with the argument's logic.
While pointing out overlooked possibilities sounds easy enough, the task can be deceptively difficult if you don't know what you're looking for. Unlike with some tasks, it is hit-or-miss on pre-phrasing answers for fails to consider assumption; this is because there are often hundreds of possibilities of reaching a different conclusion, and if you can't generalize your specific pre-phrased answer, you'll choose an attractive distractor.
To avoid this issue, we advise our clients to pre-phrase a statement of link between the inadequate evidence and the too-strong conclusion. In one of the example questions below, a good prephrase would be, "The answer will be a negation of a reason why government researchers would leave for private companies." The difference between prephrasing the gap like in the previous sentence and prephrasing an answer--like, "Government researchers don't need access to classified materials in order to conduct their research"--is that the gap will accomodate any potential answer the LSAT might throw at you, while such a specific answer prephrase causes many test-takers to be swindled by distractors. Most test takers have difficulty finding the credited response translated into LSAT speak; no sense making that process any more difficult.
At first blush, such distinctions can appear to be inconsequential; however, the LSAT gets plenty of test takers to gloss over a crucial possibility that fits in line with the evidence but not the conclusion. This test is not kind to careless readers, and the specificity of language employed is very different from everyday language.
The explanations below are for the two sample PrepTests from October 1996 and June 2007, which had a combined nine questions devoted to this type of assumption task.
Below is the frequency that this task has been asked on modern LSATs, although we are currently in the process of analyzing the pre-2007 LSAT assumption questions. It averages 4.4% of the points on a modern LSAT, and you can reasonably expect that at least four points will be devoted to finding the definition gap between the evidence and conclusion.
on LSATs since 2007
|4.4% of LR|
(2 per LSAT, range 0-5)
|?%growth from pre-2007|
Fails to consider assumption has a relatively high point-density on the LSAT. This task requires you to utilize the prerequisite skills described in argument proceeds by and main conclusion, and is often difficult for those clients with difficulties in fix by adding, strengthen, and weaken. Thus, the footprint of assumptions is larger than even the 2 points on a modern LSAT indicates.