Chapter 3 slides - Chapter 3 Descriptive Statistics...

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Chapter 3 Descriptive Statistics: Numerical Measures • Measures of Location • Measures of Variability
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Measures of Location If the measures are computed for data from a sample, they are called sample statistics . If the measures are computed for data from a population, they are called population parameters . • Mean • Median • Mode • Percentiles • Quartiles
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Mean The mean of a data set is the average of all the data values. The mean of a sample of n measurements is denoted by and equals If the data are from a population, the mean is denoted by (mu) and equals x n x x N x
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Mean – Sample mean – Population mean n = Sample Size N = Population Size n x x x n x x n n i i 2 1 1 N x x x N x N N i i 2 1 1
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Example: Table 3.1 P.96 Graduate Starting Salary 1 2850 2 2950 3 3050 4 2880 5 2755 6 2710 7 2890 8 3130 9 2940 10 3325 11 2920 12 2880
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Mean Mean: = 2850 + 2950 +…+ 2880 = 35,280 The mean of the sample is 2940. x 2940 12 280 , 35 n x x
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Median The median of a data set is the value in the middle when the data items are arranged in ascending order (smallest value to largest value). For an odd number of observations, the median is the middle value. For an even number of observations, the median is the average of the two middle values.
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Median 12 14 19 26 27 18 27 For an odd number of observations: in ascending order 26 18 27 12 14 27 19 7 observations the median is the middle value. Median = 19
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12 14 19 26 27 18 27 Median For an even number of observations: in ascending order 26 18 27 12 14 27 30 8 observations the median is the average of the middle two values. Median = (19 + 26)/2 = 22.5 19 30
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Mode The mode of a data set is the value that occurs with greatest frequency.
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This note was uploaded on 11/17/2011 for the course ECONOMICS 103 taught by Professor Tohmass during the Spring '11 term at University of Houston-Victoria.

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Chapter 3 slides - Chapter 3 Descriptive Statistics...

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