Regulars here at Ye Olde Blog know that I have posted many times about classroom grading practices. Regardless of which philosophy you ascribe to, at the end of the term, a teacher must make a decision about whether or not a student has learned (and to what extent). How much evidence is enough "to convict a student of learning," as Rick Stiggins would say? Is it by the number of assignments completed? Quality of work? Length of time information is retained? The answer is not as cut-and-dried as we might like. I have wondered if there is an answer at all.
I was pondering this particular conundrum again on Friday evening during a ScienceOnline 2010 keynote by Michael Specter, author of Denialism. The largest bone of contention amongst the crowd (and with Specter) was around how many expert opinions are "enough" to determine what the truth of the scientific matter is. For example---Is the H1N1 vaccine safe? How many doctors, virologists, physiologists, epidemic researchers, etc. must one talk to before accepting that the answer is "Yes."? Is just a doctor enough? Do you need three who agree? How much expertise is necessary for an opinion to be considered?
The struggle for some in the crowd appeared to be around defining the exact quantity of expert opinions in agreement that should be required. Others cared more about making sure the "right" experts were used. I can empathize with that sort of mental wrestling. It is similar to the questions I get from teachers at grading workshops: How many assignments should there be for each standard? Should I have three summative assessments...or five? I can never really answer their questions any more than Specter could provide a definitive answer last night about how much scientific expertise is enough. It isn't that I don't want to answer teachers or frustrate them. These questions just do not fall into black and white sorts of categories.
The danger, of course, in not thinking about guidelines and trying to get to the answer is that there continues to be wide variation in what is acceptable. Just as for one teacher, three tests and an essay is enough to say whether or not a student should receive credit for a course while other teachers need 8 tests and 5 essays, some people will accept one opinion about vaccines and others want four. Unfortunately, many of those who accept a single opinion often choose one that is not based on evidence. As Specter pointed out last night, "185,000 people died from measles last year...just no one Jenny McCarthy knew."
At some point, we all have to come to terms with balancing quantity and quality of information. While I doubt that the mothers of the 185K measles victims would share McCarthy's opinion about vaccines, it does not mean that those mothers have any more medical expertise than she. We have to make a decision about how to weigh both validity and reliability of the information we have access to, whether we are teachers looking at our gradebooks, or citizens and scientists evaluating information that impacts our health and environment. How do we determine when "enough is enough"?