ENVS178 Lecture Notes - Lecture 5: Standard Ruler, Inflection Point, Normal Distribution
12 Mar 2019
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Compare different looking data with sd as a standard ruler. Further away from the mean, the more unusual the data is. To effectively compare observations across different units of measurement. Z-score: distance of observation from mean, measured in sd. The bigger the z-score, the further away from the mean; vice versa. Positive: the observation is x sd above the mean. In a normal curve, the z-score will be 0. Shfting the data by substracting the mean. Shape of the histogram and boxplot look the same. Interpret z as sd above/below the mean. The shape of the graph can look different, eg. different bin widths. When the mean = 75; sd = 14. 25. If you have a score of 82. 5, your z-score is (82. 5-75)/14. 25 = 0. 53. When the average = 74; sd = 13. 5. If you have a score of 48. 9, your z-score is (48. 9-74)/13. 5 = -1. 86. If you have a score of 93. 8, your z-score is (93. 8-74)/13. 5 = 1. 47.
