Description Usage Arguments Value Note Author(s) Examples

This function is used by the 'oneway' function for oneway analysis of variance in case a user requests post-hoc tests using the Tukey or Games-Howell methods.

1 2 3 | ```
posthocTGH(y, x, method=c("games-howell", "tukey"),
conf.level = 0.95, digits=2, p.adjust="none",
formatPvalue = TRUE)
``` |

`y` |
y has to be a numeric vector. |

`x` |
x has to be vector that either is a factor or can be converted into one. |

`method` |
Which post-hoc tests to conduct. Valid values are "tukey" and "games-howell". |

`conf.level` |
Confidence level of the confidence intervals. |

`digits` |
The number of digits to show in the output. |

`p.adjust` |
Any valid |

`formatPvalue` |
Whether to format the p values according to APA standards (i.e. replace all values lower than .001 with '<.001'). This only applies to the printing of the object, not to the way the p values are stored in the object. |

A list of three elements:

`input` |
List with input arguments |

`intermediate` |
List of intermediate objects. |

`output` |
List with two objects 'tukey' and 'games.howell', containing the outcomes for the respective post-hoc tests. |

This function is based on a file that was once hosted at http://www.psych.yorku.ca/cribbie/6130/games_howell.R, but has been removed since. It was then adjusted for implementation in the `userfriendlyscience`

package. Jeffrey Baggett needed the confidence intervals, and so emailed them, after which his updated function was used. In the meantime, it appears Aaron Schlegel (https://rpubs.com/aaronsc32) independently developed a version with confidence intervals and posted it on RPubs at https://rpubs.com/aaronsc32/games-howell-test.

Also, for some reason, `p.adjust`

can be used to specify additional correction of *p* values. I'm not sure why I implemented this, but I'm not entirely sure it was a mistake either. Therefore, in `userfriendlyscience`

version 0.6-2, the default of this setting changed from `"holm"`

to `"none"`

(also see https://stats.stackexchange.com/questions/83941/games-howell-post-hoc-test-in-r).

Gjalt-Jorn Peters (Open University of the Netherlands) & Jeff Bagget (University of Wisconsin - La Crosse)

Maintainer: Gjalt-Jorn Peters <[email protected]>

1 2 3 4 | ```
### Compute post-hoc statistics using the tukey method
posthocTGH(y=ChickWeight$weight, x=ChickWeight$Diet, method="tukey");
### Compute post-hoc statistics using the games-howell method
posthocTGH(y=ChickWeight$weight, x=ChickWeight$Diet);
``` |

```
sh: 1: cannot create /dev/null: Permission denied
n means variances
1 220 103 3210
2 120 123 5128
3 120 143 7489
4 118 135 4737
diff ci.lo ci.hi t df p p.adjusted
2-1 20.0 -0.3 40 2.54 574 .06 .22
3-1 40.3 20.0 61 5.12 574 <.01 <.01
4-1 32.6 12.2 53 4.12 574 <.01 <.01
3-2 20.3 -2.7 43 2.27 574 .11 .32
4-2 12.6 -10.5 36 1.41 574 .50 .99
4-3 -7.7 -30.8 15 0.86 574 .83 .99
n means variances
1 220 103 3210
2 120 123 5128
3 120 143 7489
4 118 135 4737
diff ci.lo ci.hi t df p p.adjusted
2-1 20.0 0.36 40 2.64 201 .04 .18
3-1 40.3 17.54 63 4.59 176 <.01 <.01
4-1 32.6 13.45 52 4.41 203 <.01 <.01
3-2 20.3 -6.20 47 1.98 230 .20 .59
4-2 12.6 -10.91 36 1.39 236 .51 1.00
4-3 -7.7 -33.90 19 0.76 226 .87 1.00
```

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