4. The attendance at college of a group of 18 students was recorded for a 4-week period.
The number of students actually attending each of 16 classes are shown below.
| 18 | 18 | 17 | 17 |
| 16 | 17 | 16 | 18 |
| 18 | 14 | 17 | 18 |
| 15 | 17 | 18 | 16 |
- Calculate the mean and the standard deviation of the number of students attending these classes.
- Express the mean as a percentage of the 18 students in the group.
In the same 4-week period, the attendance of a different group of 20, students is shown below.
| 20 | 16 | 18 | 19 |
| 15 | 14 | 14 | 15 |
| 18 | 15 | 16 | 17 |
| 16 | 18 | 15 | 14 |
- Construct a back-to-back stem and leaf diagram to represent the attendance in both groups.
- Find the mode, median and inter-quartile range for each group of students.
The mean percentage attendance and standard deviation for the second group of students are 81.25 and 1.82 respectively.
- Compare and contrast the attendance of these 2 groups of students.