7 An environmentalist measures the mean concentration, \(c\) milligrams per litre, of a particular chemical in a group of rivers, and the mean mass, \(m\) pounds, of fish of a certain species found in those rivers. The results are given in the table.
| \(c\) | 1.94 | 1.78 | 1.62 | 1.51 | 1.52 | 1.4 |
| \(m\) | 6.5 | 7.2 | 7.4 | 7.6 | 8.3 | 9.7 |
- State which, if either, of \(m\) and \(c\) is an independent variable.
- Calculate the equation of the least squares regression line of \(c\) on \(m\).
- State what effect, if any, there would be on your answer to part (ii) if the masses of the fish had been recorded in kilograms rather than pounds. ( \(1 \mathrm {~kg} \approx 2.2\) pounds.)
- The data is illustrated in the scatter diagram. Explain what is meant by 'least squares', illustrating your answer using the copy of this diagram in the Printed Answer Booklet.
\includegraphics[max width=\textwidth, alt={}, center]{708e125e-43a8-40d8-94db-0ed80337d273-4_719_1043_961_513}