Curves on tests?

Question

I don't get why teachers curve some tests.

Answer 1

Curves help to eliminate some bias presented by the test. Say, for instance, the average class grade was a 75 with the highest being an 86. Obviously this means that either none of the students learned the material very well, which typically should be dealt with anyways, or the test wasn't acceptable. It's entirely possible for questions to be worded awkwardly, material to be placed on the test that wasn't covered in class, or that students that day were simply having a hard time. By curving tests this can be avoided.

However, most tests with altered grades are actually scaled, not curved. Curving a test means actually applying the grades to a normal curve, otherwise known as a bell curve. The teacher takes the highest grade and boosts it to a 100, and allows all other grades to fall into place along the bell curve via various statistical mathematical equations. Instead, mainly out of ease, most teachers scale a test.

Essentially, scaling is more beneficial than curving. The teacher will take the highest grade and make it a 100, and then add the difference onto every other grade. For instance, if a 95 was the highest grade, it would then become a 100. Since 100-95 = 5, all other grades would receive 5 more points. So a 70 would be a 75, an 82 would be an 87, and so on and so forth.

There are a number of reasons for curving, and it sometimes just depends on the teacher's mood or feelings towards a particular test. It's just easier to always try your best and work towards the score you want to get.