To get Row 4, we subtract the mean from each value of X:

x 50 150 250 350 450
P(X = x) .1 .3 .2 .4 0
x.P(X = x) 5 45 50 140 0 = Sum = 240
x- 50 - 240 = -190 150 - 240 = -90 250 - 240 = 10 350 - 240 = 110 450 - 240 = 210


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