qDunnett | R Documentation |
Distribution function and quantile function for the distribution of Dunnett's many-to-one comparisons test.
qDunnett(p, n0, n)
pDunnett(q, n0, n, lower.tail = TRUE)
p |
vector of probabilities. |
n0 |
sample size for control group. |
n |
vector of sample sizes for treatment groups. |
q |
vector of quantiles. |
lower.tail |
logical; if TRUE (default),
probabilities are |
Dunnett's distribution is a special case of the multivariate t distribution.
Let the total sample size be N = n_0 + \sum_i^m n_i
, with m
the
number of treatment groups, than the quantile T_{m v \rho \alpha}
is calculated with v = N - k
degree of freedom and
the correlation \rho
\rho_{ij} = \sqrt{\frac{n_i n_j}
{\left(n_i + n_0\right) \left(n_j+ n_0\right)}} ~~
(i \ne j).
The functions determines m
via the length of the input
vector n
.
Quantiles and p-values are computed with the functions of the package mvtnorm.
pDunnett
gives the distribution function and
qDunnett
gives its inverse, the quantile function.
The results are seed depending.
qmvt
pmvt
dunnettTest
## Table gives 2.34 for df = 6, m = 2, one-sided
set.seed(112)
qval <- qDunnett(p = 0.05, n0 = 3, n = rep(3,2))
round(qval, 2)
set.seed(112)
pDunnett(qval, n0=3, n = rep(3,2), lower.tail = FALSE)
## Table gives 2.65 for df = 20, m = 4, two-sided
set.seed(112)
qval <- qDunnett(p = 0.05/2, n0 = 5, n = rep(5,4))
round(qval, 2)
set.seed(112)
2 * pDunnett(qval, n0= 5, n = rep(5,4), lower.tail= FALSE)
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