PSY201H5 Lecture Notes - Lecture 5: Squared Deviations From The Mean, Standard Deviation, Variance
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Range: the diff between highest + lowest score, ex 2 3 4 6 10 --> 10-2 = 8 8. The longest + shortest wait time for bus. This gives sense of variability but it can be inflated by an outlier. = av of the squared deviations from mean. Is the bus generally on time (just a few mins early/late) or does wait time vary a lot? (could be 10 mins early or late) Care how much each step deviates from mean: 4 steps --> av of the squared deviations from the mean. Sum the squares, or compute the sum of the squared deviations. Divide ss (sum of squared deviations) by n: but the av squared deviations is a bit abstract, problem w/ variance. We want to know how much scores typically varied from mean in meaningful units. Sigma = square root (ss/n: the smaller (lower) the standard deviation --> the more reliable the mean, properties of standard deviation.
