Tom reacts to Peter Catt’s article entitled “Assessing the Cost of Forecast Error; A Practical Example.” (Published in Issue 7 of Foresight) NOTE: This is one of 3 commentaries on Catt’s article. Copyright International Institute of Forecasters, 2007

We compare two methods for dividing an interrupted time-series study between baseline and experimental phases when study resources are limited. In fixed designs the baseline duration is chosen before the baseline begins. In flexible designs the baseline duration is not predetermined but made...