Math
posted by CB .
The probability that a school bus is late is 0.04. How many times would you expect the bus to be late in a 5week period?

That's 25 school days. The average or "expectation" number of late appearances will be 25x0.04 = 1.0, but there are nonzero probabilities of 0,2,3, etc. late appearances as well. The binomial distribution can be used to calculate their probabilities.