Paper 2, Section I, H

Statistics
Part IB, 2016

The efficacy of a new medicine was tested as follows. Fifty patients were given the medicine, and another fifty patients were given a placebo. A week later, the number of patients who got better, stayed the same, or got worse was recorded, as summarised in this table:

\begin{tabular}{|l|c|c|} \hline & medicine & placebo \ better & 28 & 22 \ same & 4 & 16 \ worse & 18 & 12 \ \hline \end{tabular}

Conduct a Pearson chi-squared test of size 1%1 \% of the hypothesis that the medicine and the placebo have the same effect.

[Hint: You may find the following values relevant:

 Distribution χ12χ22χ32χ42χ52χ6299% percentile 6.639.2111.3413.315.0916.81.]\left.\begin{array}{lcccccc}\text { Distribution } & \chi_{1}^{2} & \chi_{2}^{2} & \chi_{3}^{2} & \chi_{4}^{2} & \chi_{5}^{2} & \chi_{6}^{2} \\ 99 \% \text { percentile } & 6.63 & 9.21 & 11.34 & 13.3 & 15.09 & 16.81 .\end{array}\right]