The Pooled Standard Deviation is a weighted average of standard deviations for two or more groups, assumed to have equal variance. It represents the common deviation among the groups, around each of their respective means.

## Usage

sd_pooled(x, y = NULL, data = NULL, verbose = TRUE)

mad_pooled(x, y = NULL, data = NULL, constant = 1.4826, verbose = TRUE)

## Arguments

x

A formula, a numeric vector, or a character name of one in data.

y

A numeric vector, a grouping (character / factor) vector, a or a character name of one in data. Ignored if x is a formula.

data

An optional data frame containing the variables.

verbose

Toggle warnings and messages on or off.

constant

scale factor.

## Value

Numeric, the pooled standard deviation.

## Details

The standard version is calculated as: $$\sqrt{\frac{\sum (x_i - \bar{x})^2}{n_1 + n_2 - 2}}$$ The robust version is calculated as: $$1.4826 \times Median(|\left\{x - Median_x,\,y - Median_y\right\}|)$$

cohens_d()
sd_pooled(mpg ~ am, data = mtcars)
mad_pooled(mtcars$mpg, factor(mtcars$am))