The empirical rule used in the iTunes example says that for a bell-shaped distribution, the sample mean will fall within how many standard deviations of the population mean in approximately 95% of samples?

1. The empirical rule is introduced before the exact z-based method as a rough approximation. 2. It states that in about 95% of samples, the sample mean falls within two standard deviations of the population mean. 3. For the iTunes example with standard error 0.1, two standard deviations is (2)(0.1) = 0.2, giving an approximate interval of x-bar ± 0.2. 4. Options B, C, and D each substitute a different multiple of the standard deviation than the rule actually uses. _Source: OpenStax Introductory Statistics (CC BY 4.0), Ch 8 "Confidence Intervals", section 8.1 A Single Population Mean using the Normal Distribution_