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M119L06-page14

# M119L06-page14 - The scores on a test have mean = 50 points...

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(Lesson 6: Measures of Spread or Variation; 3-3) 3.28 PART H: RANGE RULE OF THUMB Both Chebyshev’s Theorem and the Empirical Rule imply that, in terms of SDs, we can’t have too much of the data too far away from the mean. In particular, the “vast majority” of the data must lie within two SDs of the mean. (We could also use three SDs, for example.) Range Rule of Thumb for Interpreting σ The vast majority of the values in a population data set will lie between μ 2 σ and μ + 2 σ .
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Unformatted text preview: The scores on a test have mean = 50 points and SD = 10 points . The “vast majority” of the scores must lie between 30 and 70 points. Let’s say that the “realistic range” of the data set is 70 − 30 = 40 points . The idea is that few of the scores will be less than 30 points or greater than 70 points. In general, Realistic range ≈ 4 . As a result, we obtain: Range Rule of Thumb for Estimating ≈ Realistic range 4...
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