Table 2.

Expressions for ${\tilde{\sigma }}^2$ under CMD and LDD patterns for the response assuming CS(σ, ρ) for the response covariance structure, no dropout (μ_m = 0) and a constant exposure prevalence (p_ej = p_e; ∀_j = 1, … , r + 1). Results for CMD are derived for any correlation structure for the exposure while results for LDD are derived under the assumption of CS correlation structure for the exposure.

Response pattern	${\tilde{\sigma }}^2$
CMDa	$\frac{{\sigma }^2(1-\rho )}{p_e(1-p_e)}\cdot \frac{\rho r+1}{(r+1)\left[\rho \right(1-{\rho }_e)r+1-\rho ]}$
LDDb	$\frac{12{\sigma }^2(1-\rho )}{p_e(1-p_e)}\cdot \frac{(\rho r+1)r}{(r+1)\{\rho {\rho }_e{r}^2+[2\rho +{\rho }_e+3(1-\rho ){\rho }_e(1-{\rho }_e)]r+2[1+(1-{\rho }_e)(2-\rho )\left]\right\}}$
If time–invariant exposure (ρe = 1)
CMD	$\frac{{\sigma }^2}{p_e(1-p_e)}\cdot \frac{\rho r+1}{r+1}$
LDD	$\frac{12{\sigma }^2(1-\rho )}{p_e(1-p_e)}\cdot \frac{r}{(r+1)(r+2)}$

^aFor any correlation structure of exposure.

^bAssuming compound symmetry for the correlation structure of exposure.