Given the following two way table
[tex]\begin {center}
\begin {tabular}
{|c||c|c|c|}
&10-mg Atorvastatin&Placebo \\ [1ex]
Headache&15&65 \\ No Headache&17&3
\end {tabular}
\end {center}[/tex]
From the table, it can be seen that the total number of people using placebos is 65 + 3 = 68 out of a total number of 100 patients studied.
Therefore, if two different subjects are randomly selected , the probability that they both use placebos is given by
[tex] \frac{68}{100} \times \frac{68}{100} =0.68\times0.68=0.4624\approx0.46[/tex]
