Try z-scores.
z = (x - mean)/sd
Once you have the z-score, check out a z-table for your probability. (Remember that the problem is looking for "more than 13 minutes" when you determine the probability.)
ER promises you will be seen in 10 minutes. the standard deviation is 2 minutes. chance someone will wait more than 13 minutes.
i don't know what to do without a population size or sample size
1 answer
1 answer