UMD CCJS 200 - Chapter 4

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CCJS200 Book Notes Chapter 4 Measures of Central Tendency Measure of central tendency a summary descriptive statistic that captures the most typical score in a distribution of scores or the most typical value of a variable Purpose is to communicate what the central score or value is Mode The value of a variable that occurs more often than any other value the value with the greatest frequency An appropriate measure of central tendency for nominal ordinal or interval ratio level data With nominal and purely ordinal level data the mode is the only appropriate measure of central tendency Bimodal Distribution a distribution that contains two distinct modes Median The score at the 50th percentile in a rank ordered distribution of scores Thus one half of a variables values are less than the median and one half are greater than the median Steps to find the Median o Rank order all scores from lowest score to highest score o Find the position of the score x that is the median score by the following formula Median position n 1 2 This only gives you the median position to find the value of the median find the score in the position indicated by the formula in the rank ordered array of scores Key o X value of median o L lower real limit of the class interval that contains the median o Cf the cumulative frequency of the class interval just before the class interval that contains the median o F the frequency of the interval that contains the median o w the width of the class interval o n the total number of observations in the sample Mean The arithmetic average of a group of scores and is calculated as the sum of the scores divided by the total number of scores The mean is an appropriate measure of central tendency for interval ratio level data Key Steps to calculate the Mean from an Ungrouped Frequency Distribution Steps to Calculate the Mean from a Grouped Frequency Distribution

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# UMD CCJS 200 - Chapter 4

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