An aspiring medical student opens up his Step 1 score report and is elated to find that his score is 230, a 92 on the 1-100 scale! The score report indicates that the mean on the exam was 215 and the standard deviation is 20. Assuming a normal distribution, what is the most likely percentile of the student’s score?
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- 54.3%
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- 72.6%
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- 84.1%
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- 97.7%
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- 99.9%
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This question tests your understanding of cumulative percentiles and standard deviations (sigma) in the Normal Distribution. You should know that 1(sigma) = 84.1%, 2(sigma) = 97.7%, 3(sigma) = 99.9%, and of course that 0(sigma) = 50%. Here, the mean is 215 and the deviation = 15 (230-215). A deviation of 15 corresponds to a sigma of .75 (deviation / std. deviation = 15/20). Therefore, the answer must be greater than 50% (0 sigma) and less than 84.1% (1 sigma), leaving only answer choices A or B. B is closer to 1 sigma than A is, so the most likely answer is B.