When PCI_{2} is approximately normally distributed, the standard deviations calculated using simulations

can be used to test differences between actual PCI_{2} values using the following formula:

d =

ABS ( PCI

_{a}– PCI_{b})√ ( PCI

_{aSD})^{2}+ ( PCI_{bSD})^{2}

where:

The **√ **is the radical symbol for the square root of the sum of the squares

ABS = Absolute value

PCI_{a} = Observed PCI_{2} for the 1st sample or group

PCI_{b} = Observed PCI_{2} for a 2nd sample or group

PCI_{aSD} = Std. Dev. of simulated PCI_{2} distribution for 1st sample or group

PCI_{bSD} = Std. Dev. of the simulated PCI_{2} distribution for 2nd sample or group

The PCI_{2} Difference test.xls performs this calculation