Calculate μ and σ, where σ is the standard deviation, defined by the following.
σ^2 = integral between (−∞,∞) (x-μ)^2 p(x) dx
The smaller the value of σ the more tightly clustered are the values of the random variable X about the mean μ.
p(x) = 1/r e^-x/r on [0, ∞),where r > 0
μ = __________
σ = +/- ________