rpact (version 1.0.0)

getSampleSizeRates: Get Sample Size Rates

Description

Returns the sample size for testing rates in one and two samples.

Usage

getSampleSizeRates(design, ..., normalApproximation = TRUE,
  riskRatio = FALSE, thetaH0 = 0, pi1 = seq(0.4, 0.6, 0.1), pi2 = 0.2,
  groups = 2, allocationRatioPlanned = 1)

Arguments

design

The trial design.

...

Ensures that all arguments are be named and that a warning will be displayed if unknown arguments are passed.

normalApproximation

If normalApproximation = FALSE is specified, the sample size for the case of one treatment group is calculated exactly using the binomial distribution. default is TRUE.

riskRatio

If riskRatio = TRUE is specified, the sample size for one-sided testing of H0: pi1/pi2 = thetaH0 is calculated, default is FALSE.

thetaH0

The null hypothesis value. For one-sided testing, a value != 0 (or != 1 for testing the risk ratio pi1/pi2) can be specified, default is 0.

pi1

The assumed probability in the treatment group if two treatment groups are considered, or the alternative probability for a one treatment group design, default is seq(0.4, 0.6, 0.1).

pi2

The assumed probability in the control group if two treatment groups are considered, default is 0.2.

groups

The number of treatment groups (1 or 2), default is 2.

allocationRatioPlanned

The planned allocation ratio for a two treatment groups design. If allocationRatioPlanned = 0 is entered, the optimal allocation ratio yielding the smallest overall sample size is determined, default is 1.

Value

Returns a TrialDesignPlanRates object.

Details

At given design the function calculates the sample size for testing rates. In a two treatment groups design, additionally, an allocation ratio = n1Fixed/n2Fixed can be specified. If a null hypothesis value thetaH0 != 0 for testing the difference of two rates thetaH0 != 1 for testing the risk ratio is specified, the sample size formula according to Farrington & Manning (Statistics in Medicine, 1990) is used.

Examples

# NOT RUN {
# Calculate sample sizes n1Fixed, n2Fixed, nFixed, and the optimum 
# allocation ratios for a range of pi1 values when testing 
# H0: pi1 - pi2 = -0.1:
getSampleSizeRates(getDesignGroupSequential(alpha = 0.025, beta = 0.2, 
    sided = 1), groups = 2, thetaH0 = -0.1, pi1 = seq(0.4, 0.55, 0.025), 
    pi2 = 0.4, normalApproximation = TRUE, allocationRatioPlanned = 0)

# Calculate sample sizes n1Fixed, n2Fixed, nFixed, and the optimum 
# allocation ratios for a range of pi2 values when testing 
# H0: pi1 / pi2 = 1.25:
getSampleSizeRates(getDesignGroupSequential(alpha = 0.025, beta = 0.2, 
    sided = 1), groups = 2, riskRatio = TRUE, thetaH0 = 1.25, pi1 = 0.3, 
    pi2 = 0.3, normalApproximation = TRUE, allocationRatioPlanned = 1)

# }