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psci3300f2

# psci3300f2 - Formula Sheet for Exam#2 POS 3713 Spring...

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Formula Sheet for Exam #2 POS 3713 - Spring 2007 (Dr. Hensel) Note about notation: X on this sheet is the same as Xbar in lecture notes Descriptive Statistics Proportion: p = f / N (where f=frequency of cases in this category, and N=total sample size) Percentage (%) = (f/N)*100 Ratio = f1 / f2 (where f1 and f2 are the frequency of cases in each category) Rate = actual / possible (often multiplied by 100, 1000, etc. to help interpret) Percentage change = ([f2-f1] / f1)*100 (where f1=the earlier value and f2=the later value) Mean: X = " X i N (where X i refers to the individual observations and N=sample size) IQV = k ( N 2 " # f 2 ) N 2 ( k " 1) (where k = # categories, f 2 = sum of frequencies squared, N=sample size) Deviation = X i " X Sum of Squares/Sum of Squared Deviations = " ( X i # X ) 2 Variance: ! 2 = SSD/N = " ( X i # X ) 2 N Standard deviation: ! = " 2 Std error of mean = std dev of sampling dist. = " N (where ! =std dev of pop, N=sample size) Z-scores Z = X i " X s (where X i =score, X =variable mean, s=variable std dev)

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