Intro to Statistics

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Z-score

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Intro to Statistics

Definition

A z-score represents the number of standard deviations a data point is from the mean. It is used to determine how unusual a particular observation is within a normal distribution.

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5 Must Know Facts For Your Next Test

  1. The z-score formula is $z = \frac{x - \mu}{\sigma}$, where $x$ is the data point, $\mu$ is the mean, and $\sigma$ is the standard deviation.
  2. Z-scores can be positive or negative; positive indicates above the mean, while negative indicates below the mean.
  3. A z-score of 0 means the data point is exactly at the mean.
  4. Z-scores are essential for calculating probabilities and percentiles in a normal distribution.
  5. In large samples, z-scores approximate t-scores, making them useful in hypothesis testing.

Review Questions

  • What does a z-score tell you about a data point's position relative to the mean?
  • How do you calculate a z-score for a given data point?
  • Why are z-scores important when working with confidence intervals?
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