# Readings - POLI 311-Fall 2010 Topic 9 Statistics Describing...

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POLI 311-Fall 2010 Topic 9 Statistics: Describing Variables Statistics for Survey Research by Winston Jackson, pg 57-62 and 73-76 of Course Pack Descriptive statistics use: mean, standard deviation, normal distributions, Z scores, cross-classification, means across categories, correlations, and regressions. Social researchers seek to describe individual variables and examine relationships between variables. 1. Measures of Central Tendency Goal: reflect with one number a distribution of values. Central tendency is measured with the mean, the median, and the mode. a. Mean Used to typify a set of observations with a single value. It is equivalent to the average. To calculate mean you add up all the values of a variable and divide the result by the total number of cases. Ex. The mean grade on a test: 80, 82, 65, 78, 92, 99 1. Add up all the values: 80+82+65+78+92+99= 496 2. Divide result by number of cases: 496/6= 82.7 b. Median Represents the mid-point of a distribution: half the cases fall above and half the cases below this point. This is used for ordinal level variables. Step 1: arrange the cases in order from least to greatest or vice versa. Step 2: assign a number to the values

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Readings - POLI 311-Fall 2010 Topic 9 Statistics Describing...

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