lecture4 - Psych 100A Winter 2010 Lecture 4: Descriptive...

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Psych 100A Winter 2010 Lecture 4: Descriptive Statistics: Numerical summaries of data: 1.Measures of variation (cont.) 1
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Comments on measures of variation Range & IQR : Cannot be combined from several groups into an overall measure. Variance : Formula for the population variance 2 of a finite population, size N  1 2 2 x N i   Computation formula for s . 2 2 n 1 1 s 2
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Example A study of the type of sediment found at a deep-sea drilling site showed the following percentages of cement (carbonate) material in core mples: samples: 10, 21, 12, 12, 20, 13, 24, 36, 31, 18, 17, 16, 49. ind the mode mean median range Find the mode, mean, median, range, IQR and SD of these 13 measurements. 3
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List 10, 21, 12, 12, 20, 13, 24, 36, 31, 18, 17, 16, 49. Ordered list 10, 12, 12, 13, 16, 17, 18, 20, 21, 24, 31, 36, 49. a. Mode = 12 b. Mean = 279/13 = 21.5 c. Median = [(13+1)/2] th obs = 7 th obs = 18 4
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0 21 12 12 20 13 24 36 31 18 17 16 49 List 10, 21, 12, 12, 20, 13, 24, 36, 31, 18, 17, 16, 49. Ordered list 10, 12, 12, 13, 16, 17, 18, 20, 21, 24, 31, 36, 49.
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lecture4 - Psych 100A Winter 2010 Lecture 4: Descriptive...

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