rProphecy is a standalone Macintosh Universal application that calculates the Spearman-Brown 'Prophecy' formula which estimates the reliability of a test if its number of items is altered.
The Spearman-Brown 'Prophecy'formula for the estimated reliability of a test if items are added or deleted. Calculate the modified test reliability by entering the current test reliability and proportion of change.
Alternatively, calculate the proportion of change needed by entering the current and modified test reliability.
The reasonableness of this reliability estimate depends on several assumptions. Review the following references to ensure appropriate use.
rProphecy source has been developed in RealBasic.