Here's how it affects final grades:
* Higher average scores can be lowered: If the class performs exceptionally well overall, a curve will lower some grades. Even if a student earns a high raw score (e.g., 90%), their final grade might be a B or even an A- if the class average is very high. This is because the curve artificially shifts the grading scale to create a desired spread of grades.
* Lower average scores can be raised: Conversely, if the class performs poorly on average, a curve will raise some grades. A student with a raw score that would normally be a C might get a B or even a B+ due to the curve.
* Creates a predetermined distribution: The goal is often to create a specific distribution of grades, such as a certain percentage of A's, B's, C's, etc., even if the raw scores don't naturally fall into that distribution. This is sometimes done to maintain a standard level of difficulty across different sections of the same course or across different years.
* Not necessarily beneficial to all students: While it can help students whose performance is slightly below the class average, it can also hurt students who performed very well. A top student might see their A+ become a simple A after the curve.
* Different curving methods: There are various ways to curve grades, some more sophisticated than others. Simple methods might involve shifting all scores up or down by a certain number of points, while more complex methods involve fitting scores to a normal distribution.
In short, grading on a curve alters the relationship between raw scores and final grades, aiming to create a pre-determined distribution of grades, regardless of the class's absolute performance level. The impact on individual students can be positive or negative depending on their performance relative to their classmates.