epi.sssupb: Sample size for a parallel superiority trial, binary outcome

Description

Sample size for a parallel superiority trial, binary outcome.

Usage

epi.sssupb(treat, control, delta, n, power, r = 1, nfractional = FALSE, alpha)

Value

A list containing the following:

n.total: the total number of study subjects required.
n.treat: the required number of study subject in the treatment group.
n.control: the required number of study subject in the control group.
delta: the equivalence limit, as entered by the user.
power: the specified or calculated study power.

Arguments

treat: the expected proportion of successes in the treatment group.
control: the expected proportion of successes in the control group.
delta: the equivalence limit, expressed as the absolute change in the outcome of interest that represents a clinically meaningful difference. For a superiority trial the value entered for delta must be greater than or equal to zero.
n: scalar, the total number of study subjects in the trial.
power: scalar, the required study power.
r: scalar, the number in the treatment group divided by the number in the control group.
nfractional: logical, return fractional sample size.
alpha: scalar, defining the desired alpha level.

References

Chow S, Shao J, Wang H (2008). Sample Size Calculations in Clinical Research. Chapman & Hall/CRC Biostatistics Series, page 90.

Julious SA (2004). Sample sizes for clinical trials with normal data. Statistics in Medicine 23: 1921 - 1986.

Pocock SJ (1983). Clinical Trials: A Practical Approach. Wiley, New York.

Wang B, Wang H, Tu X, Feng C (2017). Comparisons of superiority, non-inferiority, and equivalence trials. Shanghai Archives of Psychiatry 29, 385 - 388. DOI: 10.11919/j.issn.1002-0829.217163.

Examples

Run this code

## EXAMPLE 1 (from Chow S, Shao J, Wang H 2008, p. 91):
## Suppose that a pharmaceutical company is interested in conducting a
## clinical trial to compare the efficacy of two antimicrobial agents 
## when administered orally once daily in the treatment of patients 
## with skin infections. In what follows, we consider the situation 
## where the intended trial is for testing superiority of the 
## test drug over the active control drug. For this purpose, the following 
## assumptions are made. First, sample size calculation will be performed 
## for achieving 80% power at the 5% level of significance.

## Assume the true mean cure rates of the treatment agents and the active 
## control are 85% and 65%, respectively. Assume the superiority
## margin is 5%.

epi.sssupb(treat = 0.85, control = 0.65, delta = 0.05, n = NA, 
   power = 0.80, r = 1, nfractional = FALSE, alpha = 0.05)

## A total of 196 subjects need to be enrolled in the trial, 98 in the 
## treatment group and 98 in the control group.

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