Comparing least-squares lines for testing level changes in interrupted time-series analysis

A likelihood ratio test of equality of coefficients of variation or relative errors for two samples of unequal size is presented. The asymptotic distribution is found and the distribution is tabled for small sizes via computer simulation. Kolmogrov-Smirnov confidence intervals are constructed on the percentiles included in the table. Power studies are also simulated and the results indicate that the test has good power for small coefficients of variation