Testing multiple variance components in linear mixed-effects models.

Testing zero variance components is one of the most challenging problems in the context of linear mixed-effects (LME) models. The usual asymptotic chi-square distribution of the likelihood ratio and score statistics under this null hypothesis is incorrect because the null is on the boundary of the parameter space. During the last two decades many tests have been proposed to overcome this difficulty, but these tests cannot be easily applied for testing multiple variance components, especially for testing a subset of them.

Y chromosome diversity among the Iranian religious groups: a reservoir of genetic variation.

Background: Iran is ethnically, linguistically and religiously diverse. However, little is known about the population genetics of Iranian religious communities.

Aim: This study was performed in order to define the different paternal components of the Iranian gene pool.