In a normal distribution, 95 percent of the data lie within how many standard deviations from the mean?

• A. One
• B. Two
• C. Three
• D. Four

Answer: (B)

In a normal distribution, the spread of values around the mean follows a predictable pattern known as the 68-95-99.7 rule. This rule tells us that about 68% of data fall within one standard deviation of the mean, about 95% fall within two standard deviations, and about 99.7% fall within three. Therefore, to capture roughly 95% of the data, you look at two standard deviations from the mean. If you want the precise cutoff, it’s actually about 1.96 standard deviations, but two is the standard rounded answer.