Question 483269
In a clinical trial 250 patients are randomly assigned to receive either a proposed stroke prevention medication ( ) or a placebo ( ) and are followed over the course of a 5-years study period. These results are given in the following table:

                                                                    
Treatment Group	Event
Stroke	No Stroke	Total
 
::::::12	108	120
 
::::::28	102	130
Total	40	210	250

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I'll assume the "12" refers to the treatment group and
the 28 is the not-treatment group.
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So p-hat = 12/120  = 0.10 for the treatment group
and p-hat = 28/130 = 0.22 for the non-treatment group
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Ho: p1-p2 = 0
H1: p1-p2 < 0
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test stat: (0.10-0.22)/sqrt[(0.1*0.9/120)+(0.22*0.78/130)] = -2.6375
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p-value = P(z < -2.6375) = 0.0042
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Conclusion: Since the p-value is less than 1%, reject
Ho at the 1% significance level.
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a.	Estimate the risk of stroke comparing those on the medication to those on placebo and interpret the result.
b.	Interpret your result in part a.
The non-treatment group is twice as liable have a stroke.
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Cheers,
Stan H.