I started this post back in April. I had an idea that needed to be remembered…it had to do with the unit of analysis; a question which often occurs in evaluation. To increase sample size and, therefore, power, evaluators often choose run analyses on the larger number when the aggregate, i.e., smaller number is probably the “true” unit of analysis. Let me give you an example.
A program is randomly assigned to fifth grade classrooms in three different schools. School A has three classrooms; school B has two classrooms; and school C has one classroom. All together, there are approximately 180 students, six classrooms, three schools. What is the appropriate unit of analysis? Many people use students, because of the sample size issue. Some people will use classroom because each got a different treatment. Occasionally, some evaluators will use schools because that is the unit of randomization. This issue elicits much discussion. Some folks say that because students are in the school, they are really the unit of analysis because they are imbedded in the randomization unit. Some folks say that students is the best unit of analysis because there are more of them. That certainly is the convention. What you need to decide is what is the unit and be able to defend that choice. Even though I would loose power, I think I would go with the the unit of randomization. Which leads me to my next point–truth.
At the end of the first paragraph, I use the words “true” in quotation marks. The Kirkpatricks in their most recent blog opened with a quote from the US CIA headquarters in Langley Virginia, “”And ye shall know the truth, and the truth shall make you free”. (We wont’ talk about the fiction in the official discourse, today…) (Don Kirkpatrick developed the four levels of evaluation specifically in the training and development field.) Jim Kirkpatrick, Don’s son, posits that, “Applied to training evaluation, this statement means that the focus should be on discovering and uncovering the truth along the four levels path.” I will argue that the truth is how you (the principle investigator, program director, etc.) see the answer to the question. Is that truth with an upper case “T” or is that truth with a lower case “t”? What do you want it to mean?
Like history (history is what is written, usually by the winners, not what happened), truth becomes what do you want the answer to mean. Jim Kirkpatrick offers an addendum (also from the CIA), that of “actionable intelligence”. He goes on to say that, “Asking the right questions will provide data that gives (sic) us information we need (intelligent) upon which we can make good decisions (actionable).” I agree that asking the right question is important–probably the foundation on which an evaluation is based. Making “good decisions” is in the eyes of the beholder–what do you want it to mean.