Question

10-mg Atorvastatin Placebo Headache 15 65 No headache 17 3 3. If two different subjects are randomly selected, find the probability that they both had a headache.

Answer 1

Answer:

0.6384

Step-by-step explanation:

Given that:

10-mg Atorvastatin Placebo Headache  15      65       No headache 17      3

Hence the total of number of patients = 15 + 65 + 17 + 3 = 100 patients

The number of patients with headache = 15 + 65 = 80 patients

Also, C(n, x) is the number of combinations in which n items can be chosen taken x at a time it is given by the formula:

$C(n,x)=\frac{n!}{(n-x)!x!}$

The the probability that if two different subjects they both had a headache = $\frac{C(80,2)}{C(100,2)}=\frac{\frac{80!}{(80-2)!2!} }{\frac{100!}{(100-2)!2!} } =\frac{3160}{4950}=0.6384$