In a normal distribution, what percent within +/-1 z-score?

In a normal distribution, what percent within +/-1 z-score?

• A. 68%
• B. 34%
• C. 95%
• D. 100%

Answer: (A)

In a standard normal distribution, about 68% of the data fall within one standard deviation of the mean (between -1 and +1). This comes from the empirical rule: roughly 34% lie between the mean and +1, and about 34% lie between the mean and -1, adding up to 68%. The remaining data are in the tails beyond ±1 standard deviation (about 31.7% in total, split roughly 15.9% in each tail).

In a standard normal distribution, about 68% of the data fall within one standard deviation of the mean (between -1 and +1). This comes from the empirical rule: roughly 34% lie between the mean and +1, and about 34% lie between the mean and -1, adding up to 68%. The remaining data are in the tails beyond ±1 standard deviation (about 31.7% in total, split roughly 15.9% in each tail).