${{\sigma }^2}_I=\frac{\sigma 2\left(i\right)}{n_i}$	item variance component
${{\sigma }^2}_O=\frac{\sigma 2\left(o\right)}{n_o}$	occasion variance component
${{\sigma }^2}_{\mathit{pI}}=\frac{\sigma 2\left(\mathit{pi}\right)}{n_i}$	person x item variance component
${{\sigma }^2}_{\mathit{pO}}=\frac{\sigma 2\left(\mathit{po}\right)}{n_o}$	person x occasion variance component
${{\sigma }^2}_{\mathit{IO}}=\frac{\sigma 2\left(\mathit{io}\right)}{n_i{n}_o}$	item x occasion variance component
${{\sigma }^2}_{\mathit{pIO}}=\frac{\sigma 2\left(\mathit{pio}\right)}{n_i{n}_o}$	residual variance component