| Exam Board | Edexcel |
|---|---|
| Module | S3 (Statistics 3) |
| Year | 2016 |
| Session | June |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Chi-squared test of independence |
| Type | Standard 2×3 contingency table |
| Difficulty | Standard +0.3 This is a standard chi-squared test of independence with a 2×3 contingency table. It requires routine application of the chi-squared formula with expected frequencies calculation, but involves no conceptual difficulty beyond the standard S3 syllabus procedure. The question explicitly guides students through the process (state hypotheses, calculate expected frequencies, perform test), making it slightly easier than average for an A-level statistics question. |
| Spec | 5.06a Chi-squared: contingency tables |
| \(A\) | \(B\) | \(C\) | |
| Influenza | 12 | 29 | 9 |
| No influenza | 15 | 23 | 22 |
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.
\begin{center}
\begin{tabular}{|c|c|c|c|}
\hline
& $A$ & $B$ & $C$ \\
\hline
Influenza & 12 & 29 & 9 \\
\hline
No influenza & 15 & 23 & 22 \\
\hline
\end{tabular}
\end{center}
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)
\hfill \mbox{\textit{Edexcel S3 2016 Q2}}