I've written an ado that provides Newcombe's and a few others' methods for risk
difference (difference between proportions). It's been lying dormant since the
last year's NESUG, waiting for the help file to be written. I'll see if I can
resurrect the project to finish it off and get it to Kit Baum over the weekend,
along with, perhaps, a similarly nearly completed command for all of Shrout &
Fleiss's intraclass correlation coefficients, and an updated Jonckheere-
Terpstra command.
Joseph Coveney
Nick Cox wrote:
>I don't think there is any question of revising
>the formula. Rather, I suspect that there is an
>excellent case for adding options to -cs- to give more
>flexibility to the user.
>
>I see the case as very similar to that of
>-ci, binomial-. There's been a long history
>of different methods here and even an increasingly
>widespread realisation that the so-called exact method
>(i.e. the Clopper-Pearson method) is often not
>as satisfactory as other methods. (In one case, the
>Wilson score method, that predates Clopper-Pearson.) On
>15 July 2003 -ci- and -cii- were extended to include
>new options -wilson-, -agresti-, and -jeffreys- for computing
>different types of binomial confidence intervals.
>
>I suggest that -cs- needs a similar work-over.
>
>Nick
>[email protected]
>
>Garry Anderson
>>
>> Thank you Roger for your suggestion of using -exactcci-
>> However, this does not calculate a risk difference and the 95% CI.
>>
>> I suppose I am suggesting to the folks at Stata that a
>> revised formula be
>> used in -csi- to calculate the 95% CI of the risk difference
>> when there is
>> a small number of observations, and one or both have a 100%
>> risk. Currently
>> it is possible for the upper bound to go beyond the
>> theoretical maximum of
>> 100% difference.
>>
>> I would appreciate opinions on this by others on the list.
>>
>> Newcombe RG (1998) Interval estimation for the difference between
>> independent proportions: comparison of eleven methods. Statistics in
>> Medicine 17: 873-890
>>
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