Hi group,
Please allow me to follow up on this question, whose original posting
was attached. For not being a mathematician, could someone show me the
steps of implementing the inverse of qdunnett in Splus. It does not look
trivia to me. Thanks in advance.
Ping Zhan
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On Mon, 2 Dec 2002, Peter Christen wrote:
> Does anyone have an idea or a solution for calculating p-values for
the
> Dunnett test?
>
> For the t-distribution, S-PLUS provides the functions qt and pt, where
> qt(p,df) calculates quantiles for a given probability and pt(q,df) the
> cumulative probability for a given quantile.
>
> Similarly, for Dunnett's test, the function qdunnett calculates
> quantiles for a given significance level. Unfortunately, the inverse
> function for calculating p-values is not available.
You can write a function to invert qdunnett via uniroot. You want to
solve t = qdunnett(p, ...) for p, where t is the observed value of the
statistic (if I understand you correctly).
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