samplesize (version 0.1-7)

n.welch.test: Sample size for Student's t-test with Welch approximation

Description

Function computes sample size for Student's t-test with Welch approximation for unequal variances

Usage

n.welch.test(power = 0.8, alpha = 0.95, mean.diff = 2, sd.est1 = 1, sd.est2 = 2.65)

Arguments

power

required power 1-beta

alpha

required Level I-error 1-alpha

mean.diff

required minimum difference between group means

sd.est1

standard deviation in group 1

sd.est2

standard deviation in group 2

Value

• sample size
  Total sample size N
• sample size n1
  sample size in group 1
• sample size n2
  sample size in group 2

References

Bock J., Bestimmung des Stichprobenumfangs fuer biologische Experimente und kontrollierte klinische Studien. Oldenbourg 1998

See Also

n.indep.t.test.neq(), n.paired.t.test(), n.indep.t.test.eq()

Examples

n.welch.test(power = 0.8, alpha = 0.95, mean.diff = 2, sd.est1 = 1, sd.est2 = 2.65)