**Select menu: Stats | Mixed Models (REML)**

This menu provides facilities for analysis of linear mixed models and estimation of variance components using the method of *residual maximum
likelihood* (REML), which is also sometimes called restricted maximum likelihood.

## Available Data

This lists data structures appropriate to the current input field. The contents will change as you move from one field to the next. Double-click a name to copy it to the current input field or type the name.

## Y-Variate

Specifies the response variate (dependent variate).

## Fixed Model

The fixed model describes imposed treatment factors and covariates for which the effect of specified levels or values are of interest. The model is described using a formula, which can combine main effects and interactions of factors and also covariates.

## Random Model

The random model is generally used to describe those factors for which the values present in an experiment can be considered drawn from some large homogeneous population. The model is described using a formula, which can combine main effects and interactions of factors and also covariates. Covariance structures and initial values for the random terms can be specified by using the following buttons:

Initial Values | For larger problems, where the data set is large or there are many model parameters to be estimated, the REML algorithm will run more efficiently if it is given good initial estimates of the variance parameters. You can specify initial values for each of the terms in the expanded Random Model by clicking on this button. |

Correlated Error Terms | Lets you define a covariance structure for random effects in the Linear Mixed Model. |

## Spline Model

Specifies terms to be added to the random model as a cubic smoothing spline. Terms may be either a variate, in which case a cubic spline is generated over the values present, or an interaction of a factor and a variate (e.g. var.fac), in which case a separate cubic spline is generated for each level of the factor. The smoothing estimate is estimated by REML.

Terms must also be specified in the fixed model to provide the linear trend.

## Interactions

Controls the level of interactions to be fitted – you can indicate either All Interactions, or just main effects (No Interactions), or indicate the level of interaction (that is, set a limit on the maximum number of factors in the treatment terms that are fitted).

## Operators

This provides a quick way of entering operators in the fixed and random model formulas. Double-click on the required symbol to copy it to the current input field. You can also type in operators directly. See model formula for a description of each.

## Action Buttons

Run | Run the analysis. |

Cancel | Close the menu without further changes. |

Options | Opens a dialog where additional options and settings can be specified for the analysis. |

Defaults | Set the menu settings back to the default settings. Clicking the right mouse on this button produces a shortcut menu where you can choose to set the options using the currently stored defaults or the Genstat default settings. |

Save | Opens a dialog where you can save results from the analysis. |

Predict | Allows you form predictions based on the current model. |

Further Output | Opens a dialog for specifying further output from the analysis and displaying residual and means plots. |

## Action Icons

Pin | Controls whether to keep the menu open when you click Run. When the pin is down , then the menu will remain open, otherwise when the pin is up , the menu will close. | |

Restore | Restore names into edit fields and default settings. | |

Clear | Clear all edit and list boxes. | |

Help | Help about this menu. |

## See Also

- Initial Values for specifying initial gamma.
- Options for specifying output options.
- Further Output for obtaining additional output after fitting a model.
- Save for saving the results from a REML analysis.
- Save REML results in a spreadsheet.
- Residual Plots for generating plots of residuals.
- Means Plots for generating plots of one- or two-way tables of means.
- REML directive for command mode use of REML, with additional options to

control the algorithm and for more sophisticated analyses. - VCOMPONENTS directive for further information about

fixed, random, and spline model terms. - Linear Mixed Models (REML) – Correlated Errors

for setting up covariance models. - REML Detect Outliers dialog for identifying outliers
- REML Power calculations dialog for calculating the power of a REML analysis.
- REML Permutation Test dialog for calculating the significance of a random term using a permutation test.