LSAT Question Stem

Which one of the following is an assumption on which the reporter's argument depends? 

Logical Reasoning Question Type

This is a Necessary Assumption question. 

Correct Answer

The correct answer to this question is B. 

LSAT Question Complete Explanation

The question type for this problem is Necessary Assumption, and it asks us to identify an assumption on which the reporter's argument depends.

First, let's analyze and summarize the argument in the passage. The reporter states that a new test has been devised that can accurately diagnose autism in children as young as 18 months old. The reporter then concludes that autistic children can now benefit much earlier in life from available treatments. In the argument, the premise is that the new test can accurately diagnose autism at 18 months, and the conclusion is that autistic children can benefit earlier from treatments.

An "Evaluate" question for this argument would be: "Can the available treatments for autism be effectively applied to children as young as 18 months old?"

Now, let's discuss the answer choices:

a) No test intended for diagnosing autism at such an early age existed before the new test was devised.

- While this statement can be inferred from the passage, it is not a necessary assumption for the conclusion that autistic children can benefit earlier from treatments. The conclusion only requires that the new test can accurately diagnose autism at 18 months, not that no other test existed before.

b) A diagnostic test that sometimes falsely gives a positive diagnosis can still provide a reasonable basis for treatment decisions.

- This is the correct answer choice. The conclusion that autistic children can benefit earlier from treatments relies on the assumption that the test can provide a reasonable basis for treatment decisions, even if it sometimes gives false positive diagnoses.

c) The new test can be used to evaluate all children, regardless of the level of development of their verbal skills.

- This answer choice is too broad and not necessary for the conclusion. The assumption needed is that the new test can evaluate children as young as 18 months old, not any child in general.

d) Those children incorrectly identified as autistic will not be adversely affected by treatments aimed at helping autistic children.

- While this statement may strengthen the argument by suggesting that falsely diagnosed children will not suffer from being treated for autism, it is not necessary for the conclusion, which focuses on autistic children benefiting earlier from treatments.

e) There was no reliable evidence that autism could affect children so young until the advent of the new test.

- The existing knowledge about autism affecting young children is irrelevant to the conclusion, which focuses on the benefit of early diagnosis and treatment. This answer choice is incorrect.

In summary, the correct answer choice is (b), as it is the necessary assumption that the diagnostic test can still provide a reasonable basis for treatment decisions despite sometimes giving false positive diagnoses. This assumption is crucial for the conclusion that autistic children can benefit earlier from available treatments.