Risk
BMJ 2008; 337 doi: https://doi.org/10.1136/bmj.a2293 (Published 30 October 2008) Cite this as: BMJ 2008;337:a2293
All rapid responses
In light of my earlier question, I apologize for mixing up my values.
The equation was meant to read:
(250/175)/(250/325)=1.86
This would no doubt be the same answer as that provided in originally
except that the interpretation and working would be different.
Competing interests:
None declared
Competing interests: No competing interests
While I agree that (d) is the best answer to the question, I am
somewhat confused by the value of the odds ratio being 1.86 and the method
which was used to obtain that value.
From my knowledge of odds ratio being the odds of an event occuring
in one group to the odds of it occuring in another group and what I
understand of the sentence 'The odds ratio for breast cancer in women
taking HRT', we are looking at 2 groups:
[x] - Group of women taking HRT
[y] - Group of women NOT taking HRT
We are then comparing the odds of women developing breast cancer in [x] to
[y] which should in my opinion lead to the equation:
(250/425)/(250/575)=1.35 instead of the one provided in (d) as the answer.
The only explanation I can think of where I went wrong is in my
interpretation of the sentence and that the groups should be:
[x] - Women with breast cancer
[y] - Women withOUT breast cancer
And then compare the odds of women taking HRT in [x] to [y] which would
give me the same answer as that provided. However, I can't see how the
original sentence could have lead to this interpretation and would
appreciate it if someone could clarify with me what they think.
Competing interests:
None declared
Competing interests: No competing interests
Re: Value for Odds Ratio
Dear Mr Ding,
I think you are confusing risk ratio with odds ratio.
You might be interested to play around with the web-browser calculator I have at www.hutchon.net
Competing interests: No competing interests