samplesize.d: Sample size estimation in the t test for means

In rpsychi: Statistics for psychiatric research

Description

samplesize.d determines the sample size, when specified the effect size to be detected, desired statistical power, and significance level. samplesize.d always specifies two-sided test.

Usage

samplesize.d(delta, power = 0.8, sig.level = 0.05)

Arguments

delta	a numeric contains the effect size (Cohen's d) to be detected
power	a numeric contains the desired statistical power (default 0.80)
sig.level	a numeric contains the significance level (default 0.05)

Value

Return a numeric containing the appropriate sample size in each group.

Author(s)

Yasuyuki Okumura
Department of Social Psychiatry,
National Institute of Mental Health,
National Center of Neurology and Psychiatry
[e-mail]

References

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

See Also

ind.t.test, ind.t.test.second

Examples

##Cohen (1988) ex.2.9
samplesize.d(delta=.20, power=.95, sig.level=.05)

Example output

Loading required package: gtools
[1] 651

rpsychi documentation built on May 1, 2019, 10:10 p.m.