This paper compares empirical type I error and power of different tests that have been proposed to assess the homogeneity of within-group variances. The main questions answered in the paper are:(1) Which tests are most effective (powerful and robust) when testing the homogeneity of variances in...

This paper proposes a test for missing at random (MAR). The MAR assumption is shown to be testable given instrumental variables which are independent of response given potential outcomes. A nonparametric testing procedure based on integrated squared distance is proposed. The statistic’s...