power_NegativeBinomial {PASSED}

Power Calculation for Comparing Two Negative Binomial Rates

Description

Compute sample size or power for comparing two negative binomial rates.

Usage

power_NegativeBinomial(n1 = NULL, n2 = NULL, power = NULL, sig.level = 0.05,
mu1 = NULL, mu2 = NULL, duration = 1, theta = NULL, equal.sample = TRUE, 
alternative = c("two.sided", "one.sided"), approach = 3)

Arguments

n1

sample size in group 1, or sample size in each group if equal.sample = TRUE

n2

sample size in group 2

power

power of test (1 minus Type II error probability)

sig.level

significance level (Type I error probability)

mu1

expected rate of events per time unit for group 1

mu2

expected rate of events per time unit for group 2

duration

(average) treatment duration

theta

theta parameter of negative binomial distribution; see rnegbin

equal.sample

equal sample sizes for two groups, see details

alternative

one- or two-sided test

approach

1, 2, or 3; see Zhu and Lakkis (2014).

Details

Exactly one of the parameters n1, n2, and power must be passed as NULL, and that parameter is determined from the others.

If equal.sample = TRUE is used, N in output will denote the number in each group.

The computations are based on the formulas given in Zhu and Lakkis (2014). See power.nb.test for more details.

Value

Object of class "power.htest", a list of the arguments (including the computed one) augmented with note and method elements.

References

H. Zhu and H. Lakkis (2014). Sample size calculation for comparing two negative binomial rates. Statistics in Medicine, 33:376-387.

Examples

# calculate power, equal sizes
power_NegativeBinomial(n1 = 20, mu1 = 1, mu2 = 2, theta = 0.8)
# calculate power, unequal sizes
power_NegativeBinomial(n1 = 80, n2 = 40, mu1 = 1, mu2 = 2, theta = 0.8)
# calculate n
power_NegativeBinomial( mu1 = 1, mu2 = 2, theta = 0.8, power = 0.8)