Chapter 4: Mathematical Expectation

Below is the same plot with the original PDF of f(x) = (1/30)e-x/30 for x>0 where the y and x-axis scales are drawn on exactly the same scale. Notice the (=30 plot has a PDF more spread out than the (=15 plot. This is because the standard deviation (and variance) is larger for the (=30 plot! ................
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