powMCTInterim: Calculate Conditional or Predictive Power for Multiple...

In DoseFinding: Planning and Analyzing Dose Finding Experiments

Calculate Conditional or Predictive Power for Multiple Contrast Test

Description

Calculates the predictive or conditional power for a multiple contrast test based on interim data, e.g. for a futility interim analysis. This function can also be applied to longitudinal endpoints, where at the time of interim analysis incomplete data is available. For more details see the vignette on longitudinal data analysis with MCP-Mod: vignette("Longitudinal Data MCP-Mod", package = "DoseFinding").

Usage

powMCTInterim(
  contMat,
  mu_0t,
  S_0t,
  S_01,
  alpha = 0.025,
  type = c("predictive", "conditional"),
  mu_assumed = NULL,
  alternative = c("one.sided", "two.sided"),
  control = mvtnorm.control()
)

Arguments

contMat	Contrast matrix to use. The individual contrasts should be saved in the columns of the matrix
mu_0t	The first stage estimates
S_0t	The covariance matrix for the first stage estimates
S_01	The covariance matrix anticipated for the estimates at study end
alpha	Significance level to use
type	Whether predictive power (for a flat prior) or conditional power should be calculated. For conditional power mu_assumed needs to be specified.
mu_assumed	Mean vector to assume for the second stage (only used when type is ‘⁠conditional⁠’). If NULL (default), the first stage estimates mu_0t are used.
alternative	Character determining the alternative for the multiple contrast trend test.
control	A list specifying additional control parameters for the ‘⁠pmvnorm⁠’ calls in the code, see also ‘⁠mvtnorm.control⁠’ for details.

Value

Numeric containing the calculated power values

References

\insertRef

bornkamp2024DoseFinding

See Also

powMCT() MCTtest(), optContr()

Examples

# Setup the scenario.
doses <- c(0, 0.5, 1, 2, 4, 8)
mods <- Mods(
  emax = c(0.5, 1, 2, 4),
  sigEmax = rbind(c(0.5, 3), c(1, 3), c(2, 3), c(4, 3)),
  quadratic = -0.1,
  doses = doses
)
w <- c(1, 0.5, 0.5, 0.5, 1, 1)
contMat <- optContr(models = mods, w = w)$contMat
sigma <- 0.3
n_final <- round(531 * w / sum(w))
n <- floor(n_final / 2)
S_0t <- diag(sigma^2 / n)
S_01 <- diag(sigma^2 / n_final)
## assumed interim estimate
mu_0t <- 0.05 * doses / (doses + 1) + rnorm(6, 0, 0.382 / sqrt(n))
## assumed mu (needed for conditional power)
mu_assumed <- 0.135 * doses / (doses + 1)

# Calculate predictive and conditional power.
powMCTInterim(
  contMat = contMat, S_0t = S_0t, S_01 = S_01, mu_0t = mu_0t,
  type = "predictive"
)
powMCTInterim(
  contMat = contMat, S_0t = S_0t, S_01 = S_01, mu_0t = mu_0t,
  type = "conditional", mu_assumed = mu_assumed
)
powMCTInterim(
  contMat = contMat, S_0t = S_0t, S_01 = S_01, mu_0t = mu_0t,
  type = "predictive", alternative = "two.sided"
)
powMCTInterim(
  contMat = contMat, S_0t = S_0t, S_01 = S_01, mu_0t = mu_0t,
  type = "predictive", control = mvtnorm.control(maxpts = 1e5)
)

DoseFinding documentation built on Oct. 16, 2026, 5:08 p.m.