the article "uncertainty estimation in railway track life-cycle cost" (j. of rail and rapid transit, 2009) presented the following data on time to repair (min) a rail break in the high rail on a curved track of a certain railway line. a normal probability plot of the data shows a reasonably linear pattern, so it is plausible that the population distribution of repair time is at least approximately normal. the sample mean and standard deviation are 249.7 and 145.1, respectively.