power.t: Power calculations for t-test

Description Usage Arguments See Also Examples

Description

Power calculations for t-test

Usage

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power.t(es = NULL, n = NULL, power = NULL, sig.level = NULL,
  ratio = 1, type = c("two", "paired", "one", "unequal"),
  alternative = c("two.sided", "left", "right"))

Arguments

es

effect size.

n

total number of observations/pairs

power

power of study

sig.level

significance level

ratio

the ratio of sample size 1 to sample size 2. Only will be used when 'type' is "unequal".

type

type of t test, must be one of "one","two" (default), "paired", or "unequal". "one" means one sample t test, which test whether the population mean is equal to a specified value. "two"/"unequal" means two sample (equal size/unequal size) t test, which is used to ascertain how likely an observed mean difference between two groups would be to occur by chance alone. "paired" means paired t-test (also called the correlated t-test and the t-test for dependent means), which is used to ascertain how likely the difference between two means that contain the same (or matched) observations is to occur by chance alone.

alternative

One- or two-sided test, must be one of "two.sided" (default), "left", "right"

See Also

ES.t.one

ES.t.two

ES.t.paired

Examples

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## one sample two sided test, calculate power
power.t(es=0.2,n=60,sig.level=0.10,type="one",alternative="two.sided")

## one sample one sided (left tail) test, calculate power
power.t(es=0.2,n=60,sig.level=0.10,type="one",alternative="left")

## one sample one sided (right tail) test, calculate power
power.t(es=0.2,n=60,sig.level=0.10,type="one",alternative="right")

## one sample two sided test, calculate sampe size
power.t(es=0.2,power=0.8,sig.level=0.05,type="one",alternative="two.sided")

## one sample two sided test, calculate effect size
power.t(n=200,power=0.8,sig.level=0.05,type="one",alternative="two.sided")

## one sample two sided test, calculate sig.level
power.t(es=0.2,n=200,power=0.8,type="one",alternative="two.sided")

## paired sample two sided test, calculate power
power.t(es=0.559,n=40,sig.level=0.05,type="paired",alternative="two.sided")

## paired sample two sided test, calculate sample size
power.t(es=0.15,power=0.8,sig.level=0.05,type="paired",alternative="two.sided")

## paired sample two sided test, calculate effect size
power.t(n=200,power=0.8,sig.level=0.05,type="paired",alternative="two.sided")

## two sample two sided test, calculate power
power.t(es=0.15,n=300,sig.level=0.05,type="two",alternative="two.sided")

## two sample two sided test, calculate sample size
power.t(es=0.15,power=0.8,sig.level=0.05,type="two",alternative="two.sided")

## two sample two sided test, calculate effect size
power.t(n=300,power=0.8,sig.level=0.05,type="two",alternative="two.sided")

## two sample (unequal size), calculate sample size
power.t(es=0.15,power=0.8,sig.level=0.05,type="unequal",ratio=2,alternative="two.sided")

power.t(es=0.1,n=3000,sig.level=0.05,type="unequal",ratio=2,alternative="two.sided")

Example output

     One-sample t test power calculation 

             es = 0.2
              n = 60
          power = 0.4555818
      sig.level = 0.1
    alternative = two.sided

NOTE: n is the number of observations


     One-sample t test power calculation 

             es = 0.2
              n = 60
          power = 0.002400866
      sig.level = 0.1
    alternative = left

NOTE: n is the number of observations


     One-sample t test power calculation 

             es = 0.2
              n = 60
          power = 0.6013403
      sig.level = 0.1
    alternative = right

NOTE: n is the number of observations


     One-sample t test power calculation 

             es = 0.2
              n = 198.1508
          power = 0.8
      sig.level = 0.05
    alternative = two.sided

NOTE: n is the number of observations


     One-sample t test power calculation 

             es = 0.1990655
              n = 200
          power = 0.8
      sig.level = 0.05
    alternative = two.sided

NOTE: n is the number of observations


     One-sample t test power calculation 

             es = 0.2
              n = 200
          power = 0.8
      sig.level = 0.04851422
    alternative = two.sided

NOTE: n is the number of observations


     Paired t test power calculation 

             es = 0.559
              n = 40
          power = 0.931511
      sig.level = 0.05
    alternative = two.sided

NOTE: n is number of *pairs*


     Paired t test power calculation 

             es = 0.15
              n = 350.7638
          power = 0.8
      sig.level = 0.05
    alternative = two.sided

NOTE: n is number of *pairs*


     Paired t test power calculation 

             es = 0.1990655
              n = 200
          power = 0.8
      sig.level = 0.05
    alternative = two.sided

NOTE: n is number of *pairs*


     Two-sample (equal size) t test power calculation 

             es = 0.15
              n = 300
          power = 0.4500203
      sig.level = 0.05
    alternative = two.sided

NOTE: n is number in *each* group


     Two-sample (equal size) t test power calculation 

             es = 0.15
              n = 698.6382
          power = 0.8
      sig.level = 0.05
    alternative = two.sided

NOTE: n is number in *each* group


     Two-sample (equal size) t test power calculation 

             es = 0.2291204
              n = 300
          power = 0.8
      sig.level = 0.05
    alternative = two.sided

NOTE: n is number in *each* group


     Two-sample (unequal size) t test power calculation 

             es = 0.15
          power = 0.8
              n = 1571.695
             n1 = 1047.797
             n2 = 523.8984
          ratio = 2
      sig.level = 0.05
    alternative = two.sided

NOTE: n is the total number of observations


     Two-sample (unequal size) t test power calculation 

             es = 0.1
          power = 0.732768
              n = 3000
             n1 = 2000
             n2 = 1000
          ratio = 2
      sig.level = 0.05
    alternative = two.sided

NOTE: n is the total number of observations

powerAnalysis documentation built on May 2, 2019, 12:40 p.m.