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Sample size for a parallel superiority trial, binary outcome.
epi.sssupb(treat, control, delta, n, r = 1, power, alpha)the expected proportion of successes in the treatment group.
the expected proportion of successes in the control group.
the equivalence limit, expressed as the change in the outcome of interest that represents a clinically meaningful diffference.
scalar, the total number of study subjects in the trial.
scalar, the number in the treatment group divided by the number in the control group.
scalar, the required study power.
scalar, defining the desired alpha level.
A list containing the following:
the total number of study subjects required.
the required number of study subject in the treatment group.
the required number of study subject in the control group.
the specified or calculated study power.
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.
# NOT RUN {
## 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,
r = 1, power = 0.80, 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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