STAT-2300 Lecture Notes - Lecture 4: Interquartile Range, Standard Deviation
13 Sep 2019
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Document Summary
Shape: look at symmetry, skewness, number of peaks, clusters, gaps or outliers. Spread: the degree that data values are clustered together or spread out (range, variance, standard deviation or interquartile range) Most common measures of center: mean and median. Mean: the sum of observations divided by the number of observations (average) Median (m): middle observation when the observations are listed in order. The median is resistant to extreme observations meaning outliers have little influence on its value. The shape of a distribution influences whether the mean is larger or smaller. Approx symmetric: mean and median are equal. If a distribution is skewed the median is preferred. If the distribution is symmetric then mean is preferred. When describing a distribution the center does not only accurately describe it, the degree of spread needs to be described as well. Spread can be measured by: range, interquartile range, variance, standard deviation.
