STATS 10 Lecture Notes - Lecture 5: Quartile, Unimodality, Summary Statistics
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Stats 10 lecture notes week 2 day 2. Guidelines--prefer mean and sd for symmetric data. The mean and sd can be used to determine z-score. The z-score of an observation is its distance from the mean, expressed in sd. In the us, the heights of adult women have a mean of 64 inches and an sd of 3 inches. If a woman has a height of 67 inches, what is her z-score. Another woman has a height of 59. 5 inches. Z-scores give a sense of how unusual an observation is. Empirical rule: (applies to many numeric sets of data, but especially true if data is unimodal and symmetric. About (~68%) of data is within 1 sd of mean (or have z-scores between -1 and 1. Heights of women: mean 64, sd 3. ~68% of women have height between 61-67. ~95% of day is within 2 sd of mean.
