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Lecture 3_central tendency

Lecture 3_central tendency - Measures of Central Tendency...

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1/10/2010 1 Measures of Central Tendency: Describing Typical Scores in the Data 1 Getting into the Specifics of the Sample • Once you have analyzed distributions and graphs to get a general understanding of scores in your data, you can compute measures of central tendency to calculate specific statistics on your sample. – The goal of central tendency is to identify a single score that is “typical” of the entire sample (or population) 2 Measures of Central Tendency • The three measures of central tendency are the mean, median, and the mode • Unfortunately, no single measure works best in every situation • Nor will they necessarily provide you with the same interpretations 3

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1/10/2010 2 Example • The following values were obtained from a survey on employee salary • The values are similar, but which one should you use? What best defines salary level in the sample? 4 Mean • The mean is the arithmetic average, or the score that each person would get if the scores were added up and divided equally – The sample mean is denoted by M – The population mean is denoted by (pronounced “mu”) • The mean does not describe the data well in the presence of extreme values: it distorts the value of the most typical score 5 Calculating the Mean • The mean is calculated by adding up all of the scores, then dividing by the total number of scores 6 n X M
1/10/2010 3 Numerical Example 7 X i 4 7 11 13 13 16 17 81 17 16 13 13 11 7 4 X X 5714 . 11 7 81 M M (n=7) Means from your Data 8 Characteristics of the Mean • Outlier scores exert an influence on the mean, such that the mean is pulled toward

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Lecture 3_central tendency - Measures of Central Tendency...

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