pwr.t2n.test

0th

Percentile

Power calculations for two samples (different sizes) t-tests of means

Compute power of tests or determine parameters to obtain target power (similar to as power.t.test).

Keywords
htest
Usage
pwr.t2n.test(n1 = NULL, n2= NULL, d = NULL, sig.level = 0.05, power = NULL,
 alternative = c("two.sided", 
        "less","greater"))
Arguments
n1

Number of observations in the first sample

n2

Number of observations in the second sample

d

Effect size

sig.level

Significance level (Type I error probability)

power

Power of test (1 minus Type II error probability)

alternative

a character string specifying the alternative hypothesis, must be one of "two.sided" (default), "greater" or "less"

Details

Exactly one of the parameters 'd','n1','n2','power' and 'sig.level' must be passed as NULL, and that parameter is determined from the others. Notice that the last one has non-NULL default so NULL must be explicitly passed if you want to compute it.

Value

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

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

Cohen, J. (1988). Statistical power analysis for the behavioral sciences (2nd ed.). Hillsdale,NJ: Lawrence Erlbaum.

Aliases
  • pwr.t2n.test
Examples
# NOT RUN {
## Exercise 2.3 p. 437 from Cohen (1988)
pwr.t2n.test(d=0.6,n1=90,n2=60,alternative="greater")
# }
Documentation reproduced from package pwr, version 1.2-2, License: GPL (>= 3)

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