Comparing Ordinal and Ratio Scale Data in Requirements Prioritisation

The importance of prioritising requirements is widely recognised. A number of different techniques for prioritising requirements have been proposed, some based on an ordinal scale, others on a ratio scale. Different scales provide different levels of information, e.g. the ratio scale is richer than the ordinal scale. This paper aims to investigate the difference in information and aim to find ways to measure and compare the different levels of information. This is important since techniques using a richer scale tend to be more time-consuming and complex to use. Thus, there is a trade-off between simple techniques yielding less information
and complex techniques yielding more information.
The paper suggests three approaches to compare the level of information inherent in the two scales, and one way to design the cost-value diagram when the priorities are based on ranks. An empirical data set was used to verify the suggested approaches.