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st: RE: Sample size calculation for dose response
A possible reference might be Newson (2004), which describes a wide
range of power calculations.
In your case, we seem to be attempting to measure ordinal correlation
between a 3-level predictor and a continuous outcome. A possible measure
of overall ordinal trend might be Somers' D, described in Newson (2002).
If you have a pilot study, then it might make sense to use that pilot
study as the basis of the power calculations, in the manner of Example 3
of Newson (2004).
I hope this helps.
Best wishes
Roger
References
Newson R. Parameters behind "nonparametric" statistics: Kendall's tau,
Somers' D and median differences. The Stata Journal 2002; 2 (1): 45-64.
Also downloadable from my website at
http://www.kcl-phs.org.uk/rogernewson/.
Newson R. Generalized power calculations for generalized linear models
and more. The Stata Journal 2004; 4(4): 379-401. Also downloadable from
my website at http://www.kcl-phs.org.uk/rogernewson/.
Roger Newson
Lecturer in Medical Statistics
POSTAL ADDRESS:
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute at Imperial College London
St Mary's Campus
Norfolk Place
London W2 1PG
STREET ADDRESS:
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute at Imperial College London
47 Praed Street
Paddington
London W1 1NR
TELEPHONE: (+44) 020 7594 0939
FAX: (+44) 020 7594 0942
EMAIL: [email protected]
WEBSITE: http://www.kcl-phs.org.uk/rogernewson/
Opinions expressed are those of the author, not of the institution.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Tun, Waimar
Sent: 13 February 2006 21:17
To: [email protected]
Subject: st: Sample size calculation for dose response
Hello.
Anyone know how to do sample size calculations for studies looking at
dose response?
Essentially, we want to see if levels of a biomarker (call it X) changes
when subjects are inseminated with varying levels of semen (10 units,
100 units, 1000 units). The biomarker X would be a continuous variable.
So I want to see the correlation between biomarker X and these 3 levels
of semen.
Any guidance would be helpful.
Thanks.
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