MCAT psych

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A student is volunteering in a hospital with a stroke center. When asked what he believes is the prevalence of stroke among those greater than 65 years old, the student states that it is probably about 40% even though data analysis indicates that it is significantly lower. What accounts for this error?

A. Deductive reasoning

B. Representativeness heuristic

C. Base rate fallacy

D. Confirmation bias


Answer is C why is it not B?

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Both the representativeness heuristic and the base rate fallacy are linked, so as you delve deeper into each concept you could make a case for both. However, a more straightforward approach is probably best here. The student is asked about the prevalence of stroke in the elderly population which is the base rate for the population. Because the student sees more stroke patients, he thinks the rate is higher.
Now if that student was presented with a new patient who had stroke-like symptoms and was asked to estimate the probability, the representativeness heuristic would play more of a role. But an overestimation here would still rely on failing to consider the base rate.

Since the question is focused on the prevalence and not on how much an individual matches a representative category, C is a better answer than B.


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Was wondering what source you found this question and what their explanation was?

My understanding of base rate fallacy was that you were already somewhat aware of the actual base rate, but prefer to rely on case-specific statistics. This question seems to at least incorporate that latter part...

Anyways, I think representative bias would be more of a situation where the student is shown a young, middle-aged, and old patient and was asked to guess which one was a stroke victim. He says the old dude because it fits the prototype/representation he has in his head of what a stroke victim would look like.
 
Was wondering what source you found this question and what their explanation was?

My understanding of base rate fallacy was that you were already somewhat aware of the actual base rate, but prefer to rely on case-specific statistics. This question seems to at least incorporate that latter part...

Anyways, I think representative bias would be more of a situation where the student is shown a young, middle-aged, and old patient and was asked to guess which one was a stroke victim. He says the old dude because it fits the prototype/representation he has in his head of what a stroke victim would look like.

it's from the kaplan psychology book!
 
A base rate fallacy is made when someone ignores known data and makes up their own based on generalizations, heuristics, or otherwise. The problem reads, "the student states that it is probably about 40% even though data analysis indicates that it is significantly lower." That is, there is previous data, yet the student ignored it and made up their own statistic. This is the definition of base rate fallacy, hence why it is the answer.

Confusing and tricky. The trick to this problem was in the wording. Hope that helped clarify it more!
 
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