Question

If two different subjects are randomly selected , find the probability that they both use placebos

Answer 1

Given the following two way table

`\begin {center} \begin {tabular} &10-mg Atorvastatin&Placebo \\ [1ex] Headache&15&65 \\ No Headache&17&3 \end {tabular} \end {center}`

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

`(68)/(100) * (68)/(100) =0.68*0.68=0.4624\approx0.46`