5 Sales of cell phones at a certain shop occur singly, randomly and independently.
- State one further condition that must be satisfied for the number of sales in a certain time period to be well modelled by a Poisson distribution.
The average number of sales per hour is 1.2 .
Assume now that a Poisson distribution is a suitable model. - Find the probability that the number of sales during a randomly chosen 12 -hour period will be more than 12 and less than 16 .
- Use a suitable approximating distribution to find the probability that the number of sales during a randomly chosen 1-month period (140 hours) will be less than 150 .