critical_t2s

The function allows to calculate cohen's d and critical d for a two samples t-test.

Usage

critical_t2s(
  m1 = NULL,
  m2 = NULL,
  t = NULL,
  sd1 = NULL,
  sd2 = NULL,
  n1,
  n2,
  se = NULL,
  df = NULL,
  var.equal = FALSE,
  hypothesis = c("two.sided", "greater", "less"),
  conf.level = 0.95
)

Arguments

m1

a number representing the mean of group 1.

m2

a number representing the mean of group 2.

t

the t value.

sd1

a number representing the standard deviation of group 1.

sd2

a number representing the standard deviation of group 2.

n1

a number corresponding to the sample size of group 1.

n2

a number corresponding to the sample size of group 2.

se

a number corresponding to the standard error.

df

degrees of freedom.

var.equal

a logical variable indicating whether to treat the two variances as being equal.

hypothesis

a character string indicating the alternative hypothesis ("less", "greater" or "two.tailed").

conf.level

the confidence level to set the confidence interval, default is set to 0.95.

Value

the output returns a d which is the Cohen's d, the critical d (dc) which is the minimum value for which to get a significant result with a given sample, the bc is the numerator of the formula from which the d is calculated, se which is the standard error, df are the degrees of freedom, then it also gives the g and gc which are respectively d and dc with Hedfer's Correction for small samples.

Examples

# critical value from summary statistics
m1 <- 0.5
m2 <- 1.0
sd1 <- 1
sd2 <- 1.5
n1 <- 30
n2 <- 35
critical_t2s(m1 = m1, m2 = m2, sd1 = sd1, sd2 = sd2, n1 = n1, n2 = n2)
#> $d
#> [1] -0.3922323
#> 
#> $dc
#> [1] 0.4977544
#> 
#> $bc
#> [1] 0.625058
#> 
#> $se
#> [1] 0.3124405
#> 
#> $df
#> [1] 59.61036
#> 
#> $g
#> [1] -0.387273
#> 
#> $gc
#> [1] 0.491461
#> 
# critical value from the t statistic
se <- sqrt(sd1^2 / n1 + sd2^2 / n2)
t <- (m1 - m2) / se
critical_t2s(t = t, n1 = n1, n2 = n2, se = se) # se only required for calculating bc
#> Warning: When var.equal = FALSE the critical value calculated from t assume sd1 = sd2!
#> $d
#> [1] -0.3981665
#> 
#> $dc
#> [1] 0.4972005
#> 
#> $bc
#> [1] 0.6243625
#> 
#> $se
#> [1] 0.3124405
#> 
#> $df
#> [1] 63
#> 
#> $g
#> [1] -0.3934044
#> 
#> $gc
#> [1] 0.4912539
#>