STAT 2040 Midterm: Test 1

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Standard deviation cannot be less than the mean absolute deviation. Measures how many standard deviations an observation is above or below the mean. Almost all observations lie within 3 standard deviations of the mean. More influenced by extreme values and skewed distributions. Outliers: any observation with a z-score greater or less than 3. The range of a data set often falls around 4-6 standard deviations. The standard deviation of a data set often falls close to the interval range/6 to interval range/4. Median: value that falls in the middle when values are ordered from smallest to largest. Best measures of variability are based on deviations from the mean. Mad (mean absolute deviation): average distance from the mean. Sample variance (s^2): squared distance from the mean. Standard deviation (s): square root of sample variance. Value of the variable such that p% of the ordered data values are at or below this value.