The percentage of a normal distribution that lies between 1 standard deviation below and 1 standard deviation above the mean is approximately 68%. This corresponds to option:

C. 68

This is derived from the empirical rule (or 68-95-99.7 rule), which tells us that:

• About 68% of the data falls within 1 standard deviation of the mean,
• About 95% within 2 standard deviations, and
• About 99.7% within 3 standard deviations.

Would you like further details or have any questions?

Here are 5 related questions you might find useful:

1. What percentage of data lies within 2 standard deviations of the mean?
2. How does the empirical rule apply to non-normal distributions?
3. What is the relationship between the mean, median, and mode in a normal distribution?
4. How do you calculate standard deviation for a given data set?
5. What does it mean if a data point lies beyond 3 standard deviations from the mean?

Tip: The empirical rule is particularly helpful in assessing the spread of data in a normal distribution without having to do complex calculations.