# Oneway anova

To compare the means in three or more independent groups, oneway analysis of variance can be used. In this example, a dataset/dataframe called `dat`

contains a categorical variable `groupingVariable`

and a continuous variable `dependentVariable`

.

## SPSS

The simplest analysis uses a function called `ONEWAY`

:

```
ONEWAY dependentVariable BY groupingVariable.
```

However, to obtain an eta^2 effect size, a plot, or to test for equality of variances, the more powerful `UNIVARIATE`

function must be used:

```
UNIANOVA dependentVariable BY groupingVariable
/PRINT=ETASQ HOMOGENEITY
/PLOT=PROFILE(dependentVariable)
/DESIGN=groupingVariable.
```

## R

To only obtain the analysis of variance results, use the `oneway`

function and only specify both variables:

```
oneway(dat$dependentVariable, dat$groupingVariable);
```

Additionally, descriptives, effect sizes, a plot, Levene’s test, and corrections for heterogeneous variances can be requested:

```
oneway(dat$dependentVariable, dat$groupingVariable,
means = TRUE, levene = TRUE,
corrections = TRUE, plot = TRUE);
```