Quantitative Literacy Practice Exam 2026 – Comprehensive Preparation Guide

In a normal distribution, the 68-95-99.7 rule, often referred to as the empirical rule, describes how data is distributed in relation to the mean and standard deviations. Specifically, the rule states that approximately 68% of the data falls within one standard deviation of the mean.

This means that if you have a dataset that follows a normal distribution, and you calculate the mean and the standard deviation, you can expect that about two-thirds of the data points will lie between the mean minus one standard deviation and the mean plus one standard deviation. This characteristic of normal distributions is fundamental in statistics and allows for various predictions and assumptions based on standard deviations.

The other percentages mentioned in the options—50%, 75%, and 80%—do not accurately reflect the distribution of data according to the 68-95-99.7 rule when it comes to one standard deviation in a normal distribution. Thus, the choice that correctly identifies the percentage of data that falls within one standard deviation is 68%.