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Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 Critical Definitions! Pattern and deviations: In any graph of data, look for an overall pattern and also for any striking deviations from that pattern. For example, outliers. Outliers: An outlier in any graph of data is an individual observation that falls outside the overall pattern of the graph. To find an outlier we use the following formula: Q1 1.5*IQR to Q3 + 1.5*IQR Any value that falls outside of that range is considered to be an outlier. 1. Find any outliers using the data from yesterday's lesson: We calculated the following: min X = 0 Q1 = 3 Med = 9 Q3 = 43 max X = 118 Outliers: Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 Overall pattern of a distribution: Think SOCS To describe the overall pattern of a distribution: a) Give the Shape, Outliers, Center, and Spread. Symmetric and skewed distributions: symmetric: skewed to the right: skewed to the left: Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 The mean and median give two different ways to describe the center of a distribution. The median is right in the middle of the ordered data, but the median ignores the size of the values at either end of the distribution. As a result, we say that the median is resistant. The mean on the other hand, incorporates every value in the data set. Therefore extreme values such as outliers can have a large effect on the mean. The standard deviation s: The standard deviation s measures the average distance of the observations from their mean. It is calculated by finding an average of the squared distances and then taking the square root. Remember that it measures the spread away from the mean and it is not a resistant measure! The variance: The variance is equal to the standard deviation squared. Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 Title Freq. Intervals Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 Period 1 Got Friends? Males 90 Females 167 237 Chapter 2 Mean, SD and Variance, SOCS and resistant measures.notebook September 25, 2015 Got Friends?
