StatisticsdrillExponential: waiting longer than a time
A statistics problem from Statisticsdrill. Solve it with one answer box, with a fresh sample on every attempt and the worked steps and spreadsheet function in the answer, and it is checked the moment you submit.
The task
The time between customer arrivals at a bank branch follows an exponential distribution with a mean of 2 minutes. What is the probability that the next one is shorter than 5 minutes? Round to 4 decimal places.
What this problem teaches
The common slip is to use the mean as the rate. EXPON.DIST takes λ, so pass 1 divided by the mean.
A hint if you get stuck
With mean m the rate is λ = 1 / m, and P(X > t) = e^(-λt) = e^(-t/m). For shorter than t, take 1 minus that.
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