10 Using the 2001 UK census results and some software, Javid intended to calculate the mean number of people who travelled to work by underground, metro, light rail or tram (UMLT) for all 348 Local Authorities. However, Javid noticed that for one LA the entry in the UMLT column is a dash, rather than a 0 . See the extract below.
| Data extract for one LA in 2001 |
| Work | | mainly at or | | from home |
| UMLT | Train | |
| 295 | - | 4 | 4 |
Javid felt that it was not clear how this LA was to be treated so he decided to omit it from his calculation.
- Explain how the omission of this LA affects Javid's calculation of the mean.
The value of the mean that Javid obtained was 2046.3.
- Calculate the value of the mean when this LA is not removed.
Javid finds that the corresponding mean for all Local Authorities for 2011 is 2860.8. In order to compare the means for the two years, Javid also finds the total number of employees in each of these years. His results are given below.
| Year | 2001 | 2011 |
| 23627753 | 26526336 |
- Show that a higher proportion of employees used the metro to travel to work in 2011 than in 2001.
- Suggest a reason for this increase.