

Monday, August 25, 2014

The Impedance Mismatch

A quiz question that tripped me up today is a perfect illustration of one of the more challenging issues in developing standards: The Impedance Mismatch.  It was a true/false question of the form:

X qualitative adverb A affects Y.

According to the text:

X qualitative adverb B affects Y.

... where the degree of qualitative adverb B is greater than the degree of A (I verified that before I submitted the quiz for grading...)

Is the statement true or false?  If false, the implication is that Y is not qualitatively affected by X at least to the degree specified in A, but that is not explicitly stated, only implied by the language of the question.  If true, it does not accurately define the degree with which X affects Y.  What is happening is that a qualitative measures of slightly, moderately or heavily is being turned into an adjective for classification which is then used in a question that then has a Boolean result.

Herein lies the rub.  We have three different ways to answer a question, qualitatively on an ordinal scale, as one item from a set of classifications, or as a Boolean value.  And we haven't even touched on the various ways in which saying "I don't know" could impact it.  When looking for information to solve a problem, the challenge is often in making sure that the question being raised is asked in the right way.  When you build your forms or your interchange standards, are you dealing with the correct representation of the variety of possible answers?  If not, you could wind up with situations that cannot be adequately represented.  On the flip side, is your representation of variety so constrained as to be widely different from the data that is captured in the system that needs to communicate to the reciever?  Is it possible to infer the answer from data that is captured, if so, you might save some effort.  Making sure that the outgoing signal from one system is aligned with the incoming requirements for the other, basically that they have matched impedance, is very important to maximize information transfer.

In this particular example, the question being asked in my case was actually "Did you understand the material on how A affects B".  The outgoing signal (from the quiz) if I truly understood it, would have focused on is the work "slightly", rather than any other word in the question.  It's subtle enough (and confusing enough) that I'd almost call this a trick question except that that only trick was that the answer was cleverly evoked to see how well I did understand it.


P.S.  This experience has provided me with a new test tasking skill that I can share: Look for qualitative adjectives in true/false questions, and test your answer against how well those apply.

P.P.S. This ends my Root Cause Analysis for how I messed up my most recent quiz.

1 comment:

  1. I recommend the book "The Heart of Enterprise" by Stafford Beer.

    This book contains a resolution to the impedance match problem in the context of a business model. It is one of the most important books I ever read, and it helped transform my career from being a merely ordinary geek.