Lecture4__8211_Chapter1 - Lecture 4 Chapter 1 Wednesday,...

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Lecture 4 – Chapter 1 Wednesday, September 3 rd
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Measures of variability ± Range is the range of values ± Formula: Range = maximum – minimum ± Example: I give a test in a class and I take a sample of 6 students. The grades are: 50, 70, 64, 94, 78, 88. ± Find the range of values.
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Variance ± Variance is roughly the average square deviation of the values in the sample from the mean ± Formula: () 2 2 1 11 n i ix x xx S s nn = ==
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Standard Deviation ± Standard deviation is roughly the average distance of all the values from the mean, or else the square root of the variance ± Formula: 2 ss =
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Steps to calculate variance and standard deviation ± Calculate the mean ± Calculate the difference of all the values from the mean ± Square the differences ± Sum all the squared differences ± Divide by n-1 (and you have the variance) ± Take the square root and you have the standard deviation
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Example ± I give a test in a class and I take a sample of 6 students. The grades are: 50, 70, 64, 94, 78, 88.
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This note was uploaded on 09/23/2009 for the course STAT 318 taught by Professor Staff during the Fall '08 term at Pennsylvania State University, University Park.

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Lecture4__8211_Chapter1 - Lecture 4 Chapter 1 Wednesday,...

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