urthermore, Clogg et al. (1992) showed that the statistical test of τ − τ’ divided by its standard error is equivalent to testing the null hypothesis, Ho: β = 0. This indicates that a significance test of the intervening variable effect can be obtained simply by testing the significance of β or by dividing τ − τ’ by the standard error in Equation 6 and comparing the value to the t distribution. Although Clogg et al.'s (1992) approach tests Ho: τ − τ’ = 0, Allison (1995) and Clogg, Petkova, and Cheng (1995) demonstrate that the derivation assumes that both X and I are fixed, which is unlikely for a test of an intervening variable.