# Re: st: What does -koopmani- output? odds ratios or risk ratios?

 From Roger Harbord To statalist@hsphsun2.harvard.edu, Duolao.Wang@lshtm.ac.uk Subject Re: st: What does -koopmani- output? odds ratios or risk ratios? Date Fri, 13 Mar 2009 22:33:23 +0000

```On Fri, Mar 13, 2009 at 6:10 PM, Maarten buis <maartenbuis@yahoo.co.uk> wrote:
>
> --- On Fri, 13/3/09, Tiago V. Pereira wrote:
>> That estimate of 4.5 is actually the risk ratio, isn´t it?
>> Or am I doing a big confusion?
>
>
> I assume you refer to this -koopmani-:
> STB-58  sg154 . Conf. int. for ratio of two binomial prop. by Koopman's method (help koopman if installed) .. . . . . . . . . . . . . .  D. Wang
>        11/00   pp.16--19; STB Reprints Vol 10, pp.244--247
>
> From the helpfile of -koopmani-: "koopman computes the confidence
> intervals for the ratio of two binomial proportions", so it is a risk
> ratio not an odds ratio.
>
> -- Maarten

-koopmani- seems to have a programming issue as well as that labelling issue:

. sysuse auto, clear
(1978 Automobile Data)

. koopmani 36 40 16 80

m ambiguous abbreviation
r(111);

. drop make

. koopmani 36 40 16 80

|            Event       |            Proportion
|       Yes          No  |     Total         Yes
-----------------+------------------------+----------------------
Group1 |        36         -14  |        22      1.6364
Group2 |        16          64  |        80      0.2000
-----------------+------------------------+----------------------
Total |        52          50  |       102      0.5098
|                        |
|      Point estimate    |  [95% Conf. Interval]
-----------------|------------------------+----------------------
Odds Ratio |         8.181818       |  7.313014    12.16772
-----------------------------------------------------------------

. drop _all

. koopmani 36 40 16 80

|            Event       |            Proportion
|       Yes          No  |     Total         Yes
-----------------+------------------------+----------------------
Group1 |        36           4  |        40      0.9000
Group2 |        16          64  |        80      0.2000
-----------------+------------------------+----------------------
Total |        52          68  |       120      0.4333
|                        |
|      Point estimate    |  [95% Conf. Interval]
-----------------|------------------------+----------------------
Odds Ratio |              4.5       |  2.939633    7.152252
-----------------------------------------------------------------

I suspect koopmani.ado would benefit from some -tempvar- or tempname-
statements.

Roger.
--
Roger Harbord
http://www.epi.bris.ac.uk/staff/rharbord.htm

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```