A set of data is normally distributed with a mean of 455 and a standard deviation of 25. What percent of the data is in the interval 405–455?

The lower endpoint is 455 − 405 = 50 points below the mean, which is 50 ÷ 25 = 2 standard deviations. In a normal distribution, about 47.7% of the data lies between 2 standard deviations below the mean and the mean, closest to 47.5%. The best answer is 47.5%.

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