Calculates Cohen's d for two sample comparisons.

effect_size_t(data, response, group, absolute = FALSE, paired = FALSE,
na.rm = TRUE)

## Arguments

data A data.frame. The response variable (dependent). The group variable, usually a factor. If set to TRUE, the absolute effect size is returned. Whether the effect should be calculated for a paired t-test, default is FALSE. If TRUE (default), missing values are dropped.

## Value

numeric of length 1.

## Details

The effect size here is Cohen's d as calculated by $$d = \frac{m_{diff}}{S_p}$$, where $$m_{diff} = \bar{x}_1 - \bar{x}_2$$ and $$S_p = \sqrt{ \frac{n_1 - 1 \cdot {s_{x_1}}^2 + n_2 - 1 \cdot {s_{x_2}}^2} {n_1 + n_2 - 2} }$$.

For paired = TRUE, $$S_p$$ is substituted by $$S_D = S_{x_1 - x_2}$$ via sd(x1 - x2).

## Examples

set.seed(42)
df <- data.frame(x = runif(100), group = sample(c("A", "B"), 100, TRUE))
effect_size_t(df, "x", "group")#> [1] -0.1694691