7. A cyber-cafe recorded how long each user stayed during one day giving the following results.
| \(0 -\) | \(30 -\) | \(60 -\) | \(90 -\) | \(120 -\) | \(240 -\) | \(360 -\) |
| Number of users | 15 | 31 | 32 | 23 | 17 | 2 | 0 |
- Use linear interpolation to estimate the median and quartiles of these data.
The results of a previous study had led to the suggestion that the length of time each user stays can be modelled by a normal distribution with a mean of 72 minutes and a standard deviation of 48 minutes.
- Find the median and quartiles that this model would predict.
- Comment on the suitability of the suggested model in the light of the new results.