minTrial function

Minimum number of trials needed for a specific level of power

Calculates minimum number of trials needed to achieve power in a meta-analysis with heterogeneity.

minTrial(
  outcome,
  mc,
  tau2,
  alpha,
  beta,
  side,
  pC = NULL,
  p1 = NULL,
  var_mc = NULL,
  var_random = NULL,
  trials = NULL
)

Arguments

• outcome: Metric of interest, options include "RR" (relative risk), "OR" (odds ratio), "RD" (risk difference) and "MD" (mean difference).
• mc: Minimal clinical relevant value provided as a numeric value. Such as 0.8 for e.g. an odds ratio of 0.8.
• tau2: Heterogeneity estimate. Can be extracted from the metaanalysis() function.
• alpha: The level of type I error as a percentage, the default is 0.05 corresponding to 5%.
• beta: The level of type II error as a percentage, the default is 0.1 corresponding to 10%.
• side: Whether a 1- or 2-sided hypothesis test is used. Options are 1 or 2.
• pC: Probability of event in control group. Only used for outcomes "RR", "OR" and "RD".
• p1: Probability of event in treatment group. Only used for outcome "RD".
• var_mc: Variance of the estimated effect when outcome is "MD". Not required for outcome types "OR", "RR" or "RD".
• var_random: Estimated variance from the random-effects meta-analysis. Used then a meta-analysis have already been made previously.
• trials: Optional argument. Number of trials of interest for to provide the number of participants needed for that exact number of trials.

Returns

Either a number (minimum required trials) or the minimum required required trials together with a matrix of required participants per trial given different number of trials.

Examples

# Minimum number of trials for a prospective meta-analysis
minTrial(outcome = "RR", pC = 0.5, mc = 0.7, tau2 = 0.05, alpha = 0.05,
beta = 0.1, side = 2)

# Minimum number of trials still needed for a retrospective meta-analysis
# Note that retrospective sample size calculations are prone to bias
ma <- metaanalysis(outcome = "RR", data = perioOxy)
ris(outcome = "RR", mc = 0.80, ma = ma, type = "retrospective", fixed = FALSE,
 beta = 0.1, alpha = 0.05, side = 2)