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Standard deviation and variance

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Learn it Standard deviation measures how spread out data are around the mean. Population standard deviation: find the mean, square each value's distance from the mean, average those squares (the variance), then take the square root.

Example: Data: 2, 4, 4, 4, 5, 5, 7, 9.

  1. Mean = 40 ÷ 8 = 5.
  2. Squared distances: 9, 1, 1, 1, 0, 0, 4, 16 → sum 32. Variance = 32 ÷ 8 = 4.
  3. Standard deviation = √4 = 2.

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