... Applied Econometrics Normal Distribution 1Applied Econometrics Lecture 1: Normal Distribution For many random variables, the probability distribution is a ... is P = 0.067. Hence the expected number of failures will be 2,000 x 0.067 = 134. Example 2 .2: What number of lamps may be expected to fail between 900 and 1,300 burning hours? Solution: ... the transformed data symmetric, and, hopefully, also more normal in shape. If so, the classical model of inference about the population mean using the sample mean as estimator can again be used....