Question

The prices of all college textbooks follow a bell-shaped distribution with a mean of $180 and standard deviation of $30. Using the empirical rule, find the percentage of all college textbooks with their prices between $120 and $240.

Answer 1

The empirical rule states that for a normal distribution, nearly all of the data will fall within three standard deviations of the mean. The empirical rule can be broken down into three parts: 68% of data falls within the first standard deviation from the mean. 95% fall within two standard deviations.

μ ± 2* SD = 180 ± 2*30 = 120, 240

120 and 240 lies within 2 standard deviation from mean.

therefore, according to emperical rule,

95% textbook having price between 120 and 240.

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