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Posted by: stak
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Posted on: 2012-02-21 19:52:51
As an undergraduate, it's easy to believe that your assignments and exams are marked based on some objective criteria and your mark in a course is strictly based on your knowledge of the material. As a teaching assistant, you come to realize the truth, which is that it's nearly impossible to come up with a set of objective criteria to mark free-form (i.e. essay-type) responses from students. Back when I was a TA, the marking schemes we got for evaluating assignments and exams were never good enough. There were always students who would put down something that was unspecified or ambiguous in the marking scheme, and we would have to use our best judgement when marking those. This was particularly true on exams.
In fact, when marking some of the larger problems on exams, one of the approaches many TA's (myself included) adopted is to first decide whether or not the student actually knows the answer. If yes, then we assume the student starts with full marks, and we deduct marks for each significant error. If the student doesn't know the answer though, we do the opposite: assume the students starts at zero, and add part marks for things they got right. This approach works pretty well in achieving the ultimate goal of the whole process, which is to separate the students who know the material from those who don't.
The part of the process I want to focus on is the first part: where the TA uses his or her best judgement to decide if the student knows the answer to the question or not. This is probably the single most important factor in the student's mark, and it is essentially a subjective decision. Having a more objective marking scheme, which covered every possible student response unambiguously, would eliminate this subjectiveness. However, it would also be impractical as it would take too much time for the instructor to create such a marking scheme, and there is no guarantee that it would actually produce better results.
I'm pretty sure that this subjectiv-ization of what are supposedly objective processes happens in a lot of places. For instance, consider driving exams. Sure, the examiner has a checklist of items and takes away points for things like not checking your blind spot, but I'd bet that the driving exam (at least ones in Ontario) are a fundamentally subjective test. If the examiner feels that you are confident, safe, and in control while behind the wheel, you pass.
A key point here is that somebody who passes the subjective test might very well fail a strictly objective test, and vice-versa. You could test a driver using video equipment to ensure they check the rearview mirror every n seconds, or turn their head x degrees when checking their blind spot. But somebody who does all that may still be unsafe on the road. The subjective test allows the examiner to ensure that the driver is following the "spirit of the law" rather than the "letter of the law" when it comes to safe driving.
I further hypothesize that this disparity in the results of subjective and objective tests applies to other domains as well. One that comes to mind is smartphone purchasing. Users buy smartphones based on subjective decisions (whichever happens to appeal to them more). If asked "why?", they will then justify their subjective decision with faked objective criteria like "this phone has feature X" or "this phone is faster". Although those statements may be true, they are like scores on a driving test: made up on the spot to justify the subjective decision.
Based on my experience, many people involved in the production of said smartphones (in engineering disciplines at least) focus on the objective metrics. They think that if they implement "feature X" or make their response time faster, they will win over those users. I don't think it works that way, though. Implementing "feature X" will just make users complain about missing "feature Y" instead, because implementing "feature X" doesn't change the outcome of their subjective decision. To do that you have to resort to psychology or other such disciplines.
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