Both Edith’s and Archie’s earnings for that 8 day period add up to $1600
each. They made the same amount. And they also have the same Mean amount:
$1600÷8 days = $200 Mean (Average) per day, which is the same amount for
both of them.
But, Edith’s earnings are much closer to the Mean than Archie’s earnings. Remember,
the Mean is just another way of saying the ‘middle of things.’ Edith’s earnings show less jumping around the average value of $200 than Archie’s. Archie’s earnings are much less predictable. You have less confidence in them. One day they are $400 and the next day they are $0. In other words, Archie’s earnings have a much greater Deviation – his earnings are farther away from the Mean even though the Mean is the same for both Edith and Archie for that 8 day period.
How do we figure out Edith’s Deviation or distance from the Mean? We just subtract each of her daily earnings from the Mean of $200. The following is adapted from Quick Review of Statistics, (p. 35):
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