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#27847
Complete Question Explanation

Flaw in the Reasoning. The correct answer choice is (B)

When an advertisement is presented in a stimulus, we should generally view its claims with some degree of initial skepticism. This stimulus states that 75% of dermatologists surveyed prefer Dermactin to all other forms of skin cream. According to the ad, this is because the makers of Dermactin consulted with dermatologists during the product’s development “to ensure…the best skin cream on the market.” This assertion incorrectly presumes that the following flawed reasoning is valid:
  • Consult with dermatologists :arrow: Ensure best skin cream
The question stem asks how the reasoning in the ad is flawed. In prephrasing this answer, we might quickly consider the flaws in the author’s reasoning:

First of all, does a consultation with dermatologists really ensure the best skin cream on the market?

Second, the argument assumes that the cited dermatologists’ preferences were based primarily on the quality of the product (for example, if the surveyed dermatologists owned stock in the company which produces Dermactin, their preferences might have been based on financial considerations).

Finally, we are not told much about the survey methods. We know nothing about how many dermatologists were surveyed, nothing about the questions asked, and nothing about the comparisons made by the survey (perhaps the respondents were given only two poor options from which to choose).

Answer choice (A): The possibility that other types of physicians might have cause to use Dermactin would not necessarily render the sample unrepresentative. Since Dermactin is a skin cream, relevant opinions in this case come from dermatologists, and these are the only opinions on which the advertisement’s claims are based.

Answer choice (B): This is the correct answer choice. Without information on the number of dermatologists surveyed, there is no way to determine the validity of the claim of 75% preference among dermatologists. We would need to know the sample size in order to determine the value of the survey results. For example, if only four dermatologists were surveyed during the development of Dermactin, then a 75% preference would only represent three opinions—hardly sufficient to draw any strong conclusions.

Answer choice (C): Since the stimulus doesn’t discuss this issue, and no presumptions are suggested regarding the relative qualifications of the various dermatologists polled, this answer choice should be eliminated.

Answer choice (D): The reasoning in the stimlulus does not rely on an appeal to the opinions of consumers with no special knowledge of skin care. While the author of the stimulus does appeal to the expertise of the consulted dermatologists, there is no appeal whatsoever to the opinions of consumers, so this choice is incorrect.

Answer choice (E): The advertisement specifically suggests “if you need a skin cream, use Dermactin.” Those people who use no skin cream have been explicitly excluded, not overlooked.
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 SGD2021
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#94225
Hello,

In any situation like this stimulus where we are given a percentage of people who prefer something, but we're not told how many people were surveyed to get that percentage, will it always be a flaw that the stimulus “fails to state the number of people surveyed, which leaves open the possibility that the sample is too small to be reliable”?
 Adam Tyson
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#94238
Not always, SGD2021, but frequently! "Unrepresentative sample" is one of the standard ways to attack any argument based on surveys, and a sample that is too small is one way in which it could be seen as unrepresentative. It could also be due to the sample being drawn from too narrow a group, like only asking dermatologists who frequently prescribe or sell the product instead of a random sampling of dermatologists.

Other problems with surveys might have to do with the questions in the survey being improperly constructed, such as suggestive or confusing questions, and respondents giving inaccurate responses (people lie or make mistakes).

One classic wrong answer regarding problems with surveys is an answer that focuses on who conducted the survey. You might be suspicious if the survey was conducted by the company that makes Dermactin, but that isn't a flaw in the survey. The only reason that would cause a problem is if they surveyed an unrepresentative group, or asked bad questions, or got inaccurate responses!
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 SGD2021
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#94322
Thank you very much! Is it correct to say that, normally on a flaw question, when our stimulus doesn’t tell us anything about how many people were surveyed and there aren't explicit clues about it being an issue, this wouldn’t be the answer: fails to state the number of people surveyed, which leaves open the possibility that the sample is too small to be reliable. However, in this case it was the answer because the stimulus is from an advertisement and the people who are writing the ad conducted the survey, so we can be a little skeptical of the number of dermatologists they questioned, particularly since they say "we consulted..."? I mainly say this because it seems that when there isn't direct evidence that a sample size is too small (just like in this stimulus), it isnt the flaw, yet in this case it was.
 Adam Tyson
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#94393
An unrepresentative sample can almost always be a good Flaw answer to a question about an argument based on a survey, unless the stimulus makes clear that the sample was representative. In that case, we would look for some other flaw, such as biased questions or inaccurate answers from the survey respondents.

The stimulus doesn't need to say anything about the sample size for that to be the flaw. This argument never said how many dermatologists were surveyed, so the number could be too small.

You should always be skeptical of every argument on the LSAT, and when a survey is conducted by a potentially biased group, that's cause for skepticism. But that is not inherently a flaw, because even a potentially biased party could conduct a valid survey! Focus on the sample, the survey construction, and the answers. And if there is another survey that gets a different result, that would also weaken the argument.

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