What percentage of people would we expect to score more than two standard deviations below the mean on an IQ test?

Question

Quizplus · Accepted Answer

In a normal distribution, about 2% of the population scores more than two standard deviations below the mean. This is a property of the empirical rule, which states that 68% of data falls within one standard deviation of the mean, 95% within two standard deviations, and 99.7% within three standard deviations, leaving 2.5% in each tail beyond two standard deviations. Since the question asks for more than two standard deviations below the mean, it's half of 5%, which is 2.5%, rounded to 2%.

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