What percentage of values falls between -1 and +1 standard deviation in a normal distribution?

In a normal distribution, approximately 68.3% of the values fall between -1 and +1 standard deviations from the mean. This is a key concept in statistics related to the empirical rule, often referred to as the 68-95-99.7 rule. The rule states that:

• About 68% of the data lies within one standard deviation from the mean,
• About 95% lies within two standard deviations,
• About 99.7% lies within three standard deviations.

This characteristic of the normal distribution helps us understand data spread and variability, making it a fundamental concept in fields such as psychology, education, and Kinesiology. Recognizing these percentages allows practitioners to make informed assumptions about the population's performance or characteristics based on sample data.