# compareMean: Compare means between 2 groups In ProjectMOSAIC/mosaic: Project MOSAIC Statistics and Mathematics Teaching Utilities

## Description

A function to calculate the difference between the means of a continuous variable for two groups.

## Usage

 `1` ```compareMean(formula, data = parent.frame(), ...) ```

## Arguments

 `formula` a formula `data` a data frame in which `x` is evaluated if `x` is a formula. Note that the default is `data=parent.frame()`. This makes it convenient to use this function interactively by treating the working environment as if it were a data frame. But this may not be appropriate for programming uses. When programming, it is best to use an explicit `data` argument – ideally supplying a data frame that contains the variables mentioned `...` other arguments

## Value

the difference in means between the second and first group

## Note

This function is now defunct. Use `diffmean()` instead.

`do()`, `compareProportion()` and `shuffle()`
 ``` 1 2 3 4 5 6 7 8 9 10 11``` ```if (require(mosaicData)) { data(HELPrct) # calculate the observed difference mean(age ~ sex, data=HELPrct) obs <- diffmean(age ~ sex, data=HELPrct); obs # calculate the permutation distribution nulldist <- do(100) * diffmean(age ~ shuffle(sex), data=HELPrct) histogram(~ diffmean, groups=(diffmean >= obs), nulldist, xlab="difference in means") } ```