1 The number of failures of a machine each week at a factory is modelled by a Poisson distribution with mean 0.45.
- Write down the variance of the distribution.
- Find the probability that there are exactly 2 failures in a week.
- State a distribution which can be used to model the number of failures in a period of 4 weeks.
- Find the probability that there are at least 2 failures in a period of 4 weeks.