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Class 18: Variance and Standard Deviation

Class 18: Variance and Standard Deviation. The Expected Value of a random variable gives the average value of the distribution The Standard Deviation shows how spread out the data is You can think of the standard deviation as “ the average distance of the data from the average ”

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Class 18: Variance and Standard Deviation

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  1. Class 18: Variance and Standard Deviation • The Expected Value of a random variable gives the average value of the distribution • The Standard Deviation shows how spread out the data is • You can think of the standard deviation as “the average distance of the data from the average” • The Variance is the square of the standard deviation • Variance of discrete random variable • Variance of continuous random variable

  2. Variance, Dispersion Variance. Dispersion Text Example1. Suppose that we put 20 slips of paper, bearing the following numbers, into a box. 2, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 6 Let X be number on a slip that is drawn, at random, from the box. We put 20 slips of paper, bearing the following numbers, into a second box and let Y be the number on a slip that is drawn, at random, from that box. 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7

  3. For X and Y from Example 1, we have

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