PASSED: power_Poisson – R documentation

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power_Poisson

Power Calculations for Test of Two Poisson Ratios

Description

Compute the power for a test of two sample means with Poisson distributions, or determine parameters to obtain a target power.

Usage

power_Poisson(n1 = NULL, n2 = NULL, lambda1 = NULL, lambda2 = NULL, 
sig.level = 0.05, power = NULL, t1 = 1, t2 = 1, RR0 = 1,
equal.sample = TRUE, alternative = c("two.sided", "one.sided"))

Arguments

`n1`	sample size in group 1, or sample size in each group if `equal.sample = TRUE`
`n2`	sample size in group 2
`lambda1`	Poisson rate for group 1
`lambda2`	Poisson rate for group 2
`sig.level`	significance level (Type I error probability)
`power`	power of test (1 minus Type II error probability)
`t1`	observed time period for group 1
`t2`	observed time period for group 2
`RR0`	the ratio of lambda2 and lambda1 under null hypothesis
`equal.sample`	equal sample sizes for two groups, see details
`alternative`	one- or two-sided test

Details

Exactly one of the parameters n1, n2, lambda1, lambda2, power, and sig.level must be passed as NULL, and that parameter is determined from the others. Notice that sig.level has non-NULL defaults, so NULL must be explicitly passed if you want to compute them.

If equal.sample = TRUE is used, n2 would be ignored and N in output denotes the number in each group.

Value

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

Note

'uniroot' is used to solve power equation for unknowns, so you may see errors from it, notably about inability to bracket the root when invalid arguments are given.

References

Gu et al. (2008). Testing the ratio of two poisson rates. Biometrical Journal: Journal of Mathematical Methods in Biosciences. 50:283-298.

Examples

# Calculate power, equal sizes
power_Poisson(lambda1 = 0.0005, lambda2 = 0.003, n1 = 2000, t1 = 2, t2 = 2)
# Calculate sample size, equal sizes
power_Poisson(lambda1 = 0.0005, lambda2 = 0.003, power = 0.8, t1 = 2, t2 = 2)
# Calculate sample size for group 2, unequal sizes
power_Poisson(
  n1 = 2000, lambda1 = 0.0005, lambda2 = 0.003, power = 0.8,
  t1 = 2, t2 = 2, equal.sample = FALSE
)

PASSED

Calculate Power and Sample Size for Two Sample Mean Tests

v1.1-0

GPL (>= 2)

Authors

Jinpu Li [aut, cre], Ryan Knigge [aut], Kaiyi Chen [aut], Emily Leary [aut]

Initial release

2021-05-11