The table below shows the distribution of parcels delivered per day by a group of 100 bicycle couriers surveyed during a busy week in Copenhagen.
| Parcels | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 |
|---|
| Frequency | 3 | 6 | 10 | 14 | 23 | 20 | 13 | 8 | 3 |
A courier is chosen at random from the group of 100 couriers.
A second courier is chosen at random from the group of 100 couriers.
The delivery times of the 100 couriers were normally distributed with a mean of 30 minutes and a standard deviation of 5 minutes.
The 100 couriers were selected for the survey by randomly choosing 100 names from the full staff list using a computer generator.