Constants for Each Variance Component
Specify constant numeric values for each variance component in the model, including the residual variance, in this field.
Note: The number of values must equal the number of Random Effects plus one (1) for the residual variance.
Observe the following rules when entering constants:
| • | Separate the values with spaces. |
| • | Specify the values in exactly the same order as the random effects, with the residual variance as the last value. |
| • | If there are no random effects in your model, then specify a single numeric value corresponding to the residual variance. |
All power calculations are conditioned on these values. That is, they are assumed to be the true values of the variance components. Larger values correspond to more variability and less power.
Tip: You can determine appropriate values by running the ANOVA or Mixed Model Analysis processes on pilot study data. Use a statistic such as the mean or a quantile from the empirical distribution. To obtain these from the _owa, _amr, or _mmr tables, click Analyze > Distribution and select variables beginning with Variance_.
To Specify Constants for Each Variance Component:
| 8 | Enter values, separated with spaces, into the Constants for Each Variance Component text field. |
| 8 | If you change your mind and would like to reset the field, click . |