🎲intro to statistics review

Normal distribution

Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025

Definition

A normal distribution is a continuous probability distribution that is symmetrical around its mean, with a characteristic bell-shaped curve. In a normal distribution, most of the data points are concentrated around the mean, and the probabilities for values further away from the mean taper off equally in both directions.

AP course connection

Topic 8.3: 8.3 A Population Proportion

Unit 8

5 Must Know Facts For Your Next Test

  1. The mean, median, and mode of a normal distribution are all equal.
  2. Approximately 68% of the data in a normal distribution falls within one standard deviation of the mean.
  3. The total area under the curve of a normal distribution is equal to 1.
  4. Normal distributions are defined by two parameters: mean ($\mu$) and standard deviation ($\sigma$).
  5. The Z-score represents the number of standard deviations a data point is from the mean.

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