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The prevalence of breast cancer is compared in two groups of women based on parity.The following data are obtained at age 70 in both groups
................................... Children
...........................Yes......................NO......
Breast cancer.....120......................180.........(300)
No Breast ca......1380....................820..........(2200)
......................(1500)...................(1000).......(2500)
Based on these data what is the Relative risk(Risk Ratio) for development of Breast cancer in childless women compared with women who have children?
A-0.67
B-1.2
C-1.5
D-1.8
E-2.25
Now i got the correct answer by calculating different ways.But is there any quick approach to it???? plz share
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goforward gave this explanation....
formula for relative risk
RR = (numerator) a / a + b divided by (denominator) c / c + d
difficulty here is only in defining who is who...
Relative risk is probability of getting disease in the exposed group compared to the unexposed group...But in this question defining who is exposed who is not a little bit difficult...
Look at this by this way:
as the question asks the relative risk ratio for development of breast cancer in childless woman compared with who hane children?
so our numerator is childless women
our denominatior is women who have children
a = childless women with breast cancer = 180
b = childless women withot brest cancer = 820
c = women who have children and have breast cancer = 120
d = women who have children and don't have breast cancer = 1380
rest is just calculation:
180 / 180 + 820 divided by 120 / 120 + 1380 = 2,25
So correct answer is
5. 2.25
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Should be 180/120 or 18/12 or 3/2 = 1.5. isn't it?..
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You find the number of women who have breast cancer and are childless....thats 180 in this case....once you have identified this number, then you just criss-cross....180 multiplied by 1380, divided by (820 * 120)
The whole trick to solve those questions quickly (according to the guy in the Kaplan Bisotat videos!) is to identify that single number you will start your calculation with, and then to criss-cross.
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Sammy i thought so too at first, but then alot of people told me I should calculate the odds ratio for that. I dont know really...what do you think? This question really confused me...I dont know what we are supposed to calculate!
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You're right Ia. This is confusing...
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(180/1000)/(120/1500)=2.25
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Technically, the relative risk is the incidence exposed divided by the incidence unexposed.
So it should be the incidence of childless women with breast cancer divided by the incidence of women with breast cancer who have children. Which is what you did Sammy.
But for some reason, everyone thinks we should calculate the odds ratio?!
I dont know. I am confused :/
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Redstorm has put it in a very fine way. I got it. It's not that tough afterall.Thanks Storm
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this is prospective study. for retrospective study, use OR = (180/820)/(120/1385)
