For multilevel models with lower-level path coefficients that vary randomly at a higher level, Kenny, Korchmaros, and Bolger (2003) warn that calculation of the indirect path must consider the covariance between the higher-level random effects.
The effect of county was investigated by the introduction of an additional higher-level random effect into the model and models were similarly compared using the DIC.
Overall model fit, including the necessity for interaction terms, was ascertained using likelihood ratio statistics.[ 21] Tests of mixed (i.e., hierarchical or random effects) models,[ 22] where census tract was defined as a higher-level random effect, produced no evidence of clustering at the census tract level, indicating that the fixed effects approach was adequate.
Voxel time series were z-score-normalized for each run and the signal for the events of interest was extracted for the individual ROIs and subjected to statistical higher level group random-effects analyses.
In addition to non-random selection for oncogenic mutations, cancer cells accumulate even higher levels of random "passenger" mutations.
Additionally, students in classes using higher levels of random call reported a greater increase in their comfort level with participating in class discussions (Dallimore et al. 2013).
A second hypothesis is that periodic droughts may have cut down genetic variation across historical times [54]; in dry years, rain-splash and moisture may not be sufficient to produce dense epidemics, resulting in lower population sizes and therefore in higher levels of random genetic drift.
For example, higher levels of random error will weaken evidence of a relationship between a best practice intervention and a desired outcome and it may also create false regional differences in resource intensity or quality of care.
The estimates of genetic differentiations among four groups present in three data sets were less affected, as the Φst statistics were considerably stable over variable levels of missingness, although increased standard deviations were observed at the higher levels of random missing.
Still, the results show a high level of random variation and high error rates.
