The Mosier composite formula is computed as:

$$\rho_{XX}=\frac{\bar{\rho}_{x_{i}x_{i}}k+k\left(k-1\right)\bar{\rho}_{x_{i}x_{j}}}{k+k\left(k-1\right)\bar{\rho}_{x_{i}x_{j}}}$$

where \(\bar{\rho}_{x_{i}x_{i}}\) is the mean reliability of variables in the composite, \(\bar{\rho}_{x_{i}x_{j}}\) is the mean intercorrelation among variables in the composite, and *k* is the number of variables in the composite.