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Thread: interpretation of a negative risk difference

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    interpretation of a negative risk difference




    Hi,
    I am reviewing a cohort study and trying to make sense of the results. When considering mortality they presented their results as a risk difference which is a little different to what I normally see. Usually reported is RR or OR. In this case the results give a negative number. -35% (95%CI -50 to -21). (risk 100 of 238 with intervention, 31 of 40 with control). Am I to interpret this that there is a 35% absolute risk reduction in mortality with receiving the intervention? Ignore it's negative as simply meaning falling on the intervention side where 1 is the line of no significance? I know the confidence intervals are broad and probably show a lack of precision in measuring the treatment effect.

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    Re: interpretation of a negative risk difference


    So instead of dividing risks they subtract them, common though not as common as RR.

    CI needs to exclude "0" since it is subtraction instead of division!
    Stop cowardice, ban guns!

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