EC255 Lecture Notes - Lecture 4: Variance, Square Root, Average Absolute Deviation
Document Summary
Chapter 3: descriptive statistics (part 2: summations are just a number that is the sum of something, = sigma = sum, formulas are provided in exams. Measures of variability: ungrouped data: used to indicate how much the observations are spread out around the mean, common measures, range, mean absolute deviation, variance, standard deviation, coefficient of variation. Range: difference between the largest and smallest, ex. 0, 1, 2, 4, 6, 7, 14: the range would be (14 1 ) = 13. Deviation from the mean: how far away the observations are from the mean. If the mean = = 13 and x = the observation, the deviation from the mean is x - . If the deviation from the mean is to the left, it"ll (cid:271)e (cid:374)egati(cid:448)e: deviations to the right of the mean are positive, sum is 0. If (cid:455)ou add the de(cid:448)iatio(cid:374)s f(cid:396)o(cid:373) the (cid:373)ea(cid:374) (cid:455)ou"ll get 0: average of deviations is also 0.
