STAT 206 Lecture Notes - Lecture 6: Descriptive Statistics, Percentile, Standard Deviation
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Z-score: difference between indicated value and the mean of your data, divided by the standard deviation (x-xbar) If positive, value =is above the mean. Z3. 00 indicates an outlier value o. Skewness: extent to which data values are not symmetrical to the mean. Symmetric: if right and left sides of histogram are approximate mirror images of each other: use the mean to describe data. Skewed to the right: if the right tail extends much farther out than the left tail: also called positively skewed, use median to describe data. Skewed to the left: if the left tail extends much farther out that the right tail: also called negatively skewed, use median to describe data. Uniform: if all bars are the same height. Bimodal: if two bars are higher than others o. Percentile: the pth percentile is a value such that p percent of the observations fall below or at that value.
