6. A school introduced a new programme of support lessons in 1994 with a view to improving grades in GCSE English. The table below shows the number of years since 1994, n, and the corresponding percentage of students achieving A to C grades in GCSE English, \(p\), for each year.
| \(n\) | 1 | 2 | 3 | 4 | 5 | 6 |
| \(p ( \% )\) | 35.2 | 37.1 | 40.6 | 39.0 | 43.4 | 44.8 |
- Represent these data on a scatter diagram.
You may use the following values.
$$\Sigma n = 21 , \quad \Sigma p = 240.1 , \quad \Sigma n ^ { 2 } = 91 , \quad \Sigma p ^ { 2 } = 9675.41 , \quad \Sigma n p = 873 .$$
- Find an equation of the regression line of \(p\) on \(n\) and draw it on your graph.
- Calculate the product moment correlation coefficient for these data and comment on the suitability of a linear model for the relationship between \(n\) and \(p\) during this period.