# Facebook wallposts summary statistics measures of

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Unformatted text preview: e Correct Charts &amp; the Area Principle 0 Mean Salaries at a Major University, 2002 - 2005 20000 40000 60000 Correct Charts &amp; the Area Principle 02 03 04 05 Graphs for Quantitative Variables Histogram To make a histogram: 1.  Divide the range of the data set into equal intervals. 2.  For each interval draw a bar with the base covering the interval and the height proportional to the the count of observations that fall into the interval. #.Facebook- Wallposts Summary Statistics: Measures of Center v༇  Summary Statistics q༇  Numerical Descriptions of Distributions. q༇  Measures of center: Ø།  MODE: ü༏  Categorical variable: category with highest frequency. ü༏  Numerical variable: location of a major peak of the distribution. Ø།  MEDIAN: Middle Value . ü༏  Which value is the 50th Percentile. Ø།  MEAN: AVERAGE MEAN: More detail (and the Σ notation) v༇ Example: Consider data for a variable is 6, 9, 8, 3, 3, 1. 6 + 9 + 8 + 3 + 3 +1 Mean of the variable = =5 6 v༇ For a variable x with n observed values x1 , x2 ,..., xn the mean of x is given by: n x1 + x2 + + xn x= = n ∑x i i =1 n Median: the 50th Percentile Arrange data in order. Median Md = 50th percentile = “middle observation” [if number of observations is even, average the middle two.] E.g. for data 1, 3, 3, 6, 8 Md = 3 E.g. for data 1, 3, 3, 6, 8, 9 Md = (3 + 6) / 2 = 4.5 “Robust” or “resistant” v༇ Robust = insensitive to a few extreme observations (imagine a typo of adding several zeros to a number) v༇ Which is more robust: mean or median ? Compare 1, 3, 3, 6, 8 to 1, 3, 3, 6, 8000000 v༇ Comparison of 3 different measures of center MEASURES Applicable for Variable Uniq...
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