# REML Variance Component Estimates

This is the variation that is not explained by the model in terms of the factors.

## Block

Block variance is only present when blocks are included in the design. This is variation that is attributed to something changing that is not a factor in the experiment. It is removed from the tests and $$R^2$$ approximations.

## Group

Re-setting a hard to change factor provides a source of variation. The test for the whole plot effects is a function of both the group and residual variances. When the group variance is zero, the whole-plot model is explaining all of the variation between groups. If this occurs the analysis will be equivalent to a randomized design.

## Residual

Each run creates a source of variation separate from and in addition to the above sources. The test for subplot effects is a function of the residual variance along with the covariance with the groups.

## Total

The sum of the above sources of variation.

The estimated variance components have a standard error associated with them. The standard error is used to compute the variance confidence intervals. For blocks and groups the intervals are based upon a normal distribution. For the residual, the interval is a $$\chi^2$$ based interval.