Details
| Original language | English |
|---|---|
| Pages (from-to) | 289-292 |
| Number of pages | 4 |
| Journal | Pharmaceutical statistics |
| Volume | 10 |
| Issue number | 4 |
| Publication status | Published - 11 Oct 2010 |
Abstract
Under certain conditions, many multiple contrast tests based on the difference of treatment means can also be conveniently expressed in terms of ratios. In this paper, a Williams test for trend is defined as ratios-to-control for ease of interpretation and to obtain directly comparable confidence intervals. Simultaneous confidence intervals for percentages are particularly helpful for interpretations in the case of multiple endpoints. Methods for constructing simultaneous confidence intervals are discussed under both homogeneous and heterogeneous error variances. This approach is available in the R extension package mratios. The proposed method is used to test for trend in an immunotoxicity study with several endpoints as an example.
Keywords
- multiple comparison, ratio-to-control, Williams trend test
ASJC Scopus subject areas
- Mathematics(all)
- Statistics and Probability
- Pharmacology, Toxicology and Pharmaceutics(all)
- Pharmacology
- Medicine(all)
- Pharmacology (medical)
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In: Pharmaceutical statistics, Vol. 10, No. 4, 11.10.2010, p. 289-292.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - A ratio-to-control Williams-type test for trend
AU - Hothorn, Ludwig A.
AU - Djira, Gemechis D.
PY - 2010/10/11
Y1 - 2010/10/11
N2 - Under certain conditions, many multiple contrast tests based on the difference of treatment means can also be conveniently expressed in terms of ratios. In this paper, a Williams test for trend is defined as ratios-to-control for ease of interpretation and to obtain directly comparable confidence intervals. Simultaneous confidence intervals for percentages are particularly helpful for interpretations in the case of multiple endpoints. Methods for constructing simultaneous confidence intervals are discussed under both homogeneous and heterogeneous error variances. This approach is available in the R extension package mratios. The proposed method is used to test for trend in an immunotoxicity study with several endpoints as an example.
AB - Under certain conditions, many multiple contrast tests based on the difference of treatment means can also be conveniently expressed in terms of ratios. In this paper, a Williams test for trend is defined as ratios-to-control for ease of interpretation and to obtain directly comparable confidence intervals. Simultaneous confidence intervals for percentages are particularly helpful for interpretations in the case of multiple endpoints. Methods for constructing simultaneous confidence intervals are discussed under both homogeneous and heterogeneous error variances. This approach is available in the R extension package mratios. The proposed method is used to test for trend in an immunotoxicity study with several endpoints as an example.
KW - multiple comparison
KW - ratio-to-control
KW - Williams trend test
UR - http://www.scopus.com/inward/record.url?scp=79960819674&partnerID=8YFLogxK
U2 - 10.1002/pst.464
DO - 10.1002/pst.464
M3 - Article
C2 - 20936714
AN - SCOPUS:79960819674
VL - 10
SP - 289
EP - 292
JO - Pharmaceutical statistics
JF - Pharmaceutical statistics
SN - 1539-1604
IS - 4
ER -