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Avoiding Bias

Grading biases

Let's say Mrs. Smith is teaching a science class and has to give a grade to Charles, who has piercings on his face, a bizarre haircut, wears clothes she finds hideous, and has an unpleasant personality. She recognizes that none of these should influence the grade he gets in the science class: that is supposed to be a measure of his knowledge and ability in science only. If she judges his performance on class participation, she will find it very hard to exclude her bias, since he annoys her whenever he participates, whether his science knowledge is valid or not. If he makes a minor error in terminology she takes it as a sign of ignorance, while if Ryan, a neat and polite boy she likes, makes a similar mistake, she treats it as a triviality. The same can be true of their answers on essay tests.

Objective tests

A standard way of avoiding bias in this kind of situation is the use of "objective" tests. These are tests designed so that the answer to each question is graded according to a strict rule that will not vary from student to student and there is no opportunity for the grader to make a judgment that would be influenced by the student's personal characteristics. Multiple choice tests are very effective in this respect as well as questions with a number or particular word as an answer.

Objective tests have important drawbacks in that they are more difficult to devise, and they can't be used to test some important abilities such as engaging in group discussions or doing creative work. Nevertheless, they can help reduce or eliminate bias by making grading choices automatic. They have the additional advantage of being easy to grade and can often be graded by machine.

Hiding information

Even when the test is not objective, bias can be reduced by having someone grade the test who does not know the students. One could go to various extremes by having tests typed in order to eliminate bias based on handwriting and having names replaced by codes to remove recognition of the individual or the person's ethnicity. Bias is eliminated by only providing certain information to the person making the judgment. Information that is irrelevant to the grade is kept secret in order to prevent it from influencing the decision.

The technique of hiding information from the person making the decision can be used in many other important situations. In evaluating products, particularly food and drinks, we can easily be biased by assumptions that the product that costs more is better, or by advertising that associates the product with an image, such as being high-class and sophisticated or being rugged or rebellious. If we really want to know how we would like these products without the biases, we can arrange to try them without knowing the brand. We could have someone else give us samples of wine or soda or ice cream without knowing which brand it is so we could make our judgment purely on the basis of taste. Although we rarely will do this because it involves a lot of extra work, we should be aware that judgments based on these so-called "blind" tests are often quite different from the ones we make when we are influenced by the biasing information (see suggestion).

Of course, as with grading students, there are some cases where there is no easy way to eliminate biasing information about products. It is generally impossible to test drive a car without knowing the manufacturer.

Doing blind tests is important for scientists doing experiments requiring subjective judgments. People taking an experimental medicine, for example, could be biased towards saying they felt better if they knew the researcher giving them the medicine was enthusiastic about its possibilities. This could ruin the experiment because a useless treatment might look like it was effective. To prevent this, such tests are done so the patient cannot tell whether she is getting the real drug being tested or a fake substitute (see blinding).


Sometimes when people are unwilling or unable to eliminate biasing information they try to compensate for their biases by giving a better or worse evaluation in the opposite direction of the bias. If I don't like a students poem because he used it to promote a religious opinion I disagree with, I might increase his grade by a category because I assume my subjective assessment was unfairly low. I could also assume a car I am tempted to buy is probably not as good as I think it is because I know I was impressed by the advertising. Unfortunately this kind of compensation is a very crude and unreliable way to judge things, since we have no way of knowing just how strong our biases are.

Abstraction and role reversal

Sometimes it is useful to translate real situations into abstract terms in order to reduce our biases. For example, instead of "Harry told me he would give me his old computer but he decided to give it to his sister instead", we might judge the situation more fairly if we think of "Person one told person two that he would give him an object, but person one decided to give it to his sibling instead". Among other things, I can get a fairer view if I imagine someone other than myself involved.

A very useful and well-known method of removing bias when it involves conflict with another person is to imagine the roles being reversed. I tend to get upset when my wife tells me I did something wrong, even though it is clear that I did foul up. I feel like she should just keep quiet about it. But if I imagine myself in her position, I can easily see that she has every right to say that, especially given that it usually involves a problem that she needs to have corrected.

It is common for us to get upset at a store owner because she is charging too much for a product we want. If we imagine ourselves in the position of the owner, however, we recognize that we put in a lot of work and have a lot of expenses and need to make a living, so we have to mark up our products enough to make a living. One place where this seems very appropriate is coffee shops, where coffee costs many times what the ingredients must cost. When I consider all the costs these places have, including the salaries of the workers, instead of being upset at the high prices I become impressed that they stay in business at all, and in fact I notice that a lot of these places are no longer open after a year or so.