What percentage of the population falls within +/- one standard deviation of the mean?

The correct answer is that approximately 68% of the population falls within +/- one standard deviation of the mean in a normal distribution. This concept is grounded in the empirical rule, also known as the 68-95-99.7 rule, which describes how data is distributed in a bell-shaped curve.

In a normal distribution, the mean, median, and mode are all equal, and as you move away from the mean, the frequency of data points decreases. The first standard deviation from the mean encapsulates a significant portion of the data. Specifically, about 68% of the observations are expected to lie within one standard deviation above and below the mean. This statistic provides a quick way to gauge the spread of data and understand the likelihood of an event occurring within this range.

Thus, when interpreting a normal distribution, knowing that approximately 68% of the data falls within this interval is essential for understanding variability and making predictions about the population being studied.