- (a) State two reasons why stratified sampling might be a more suitable sampling method than simple random sampling.
(b) State two reasons why stratified sampling might be a more suitable sampling method than quota sampling. - A new drug to vaccinate against influenza was given to 110 randomly chosen volunteers. The volunteers were given the drug in one of 3 different concentrations, \(A , B\) and \(C\), and then were monitored to see if they caught influenza. The results are shown in the table below.
| \cline { 2 - 4 }
\multicolumn{1}{c|}{} | A | B | C |
| Influenza | 12 | 29 | 9 |
| No influenza | 15 | 23 | 22 |
Test, at the \(10 \%\) level of significance, whether or not there is an association between catching influenza and the concentration of the new drug. State your hypotheses and show your working clearly. You should state your expected frequencies to 2 decimal places.
(10)