Bell curve grading
Encyclopedia
In education
, grading on a curve (also known as curved grading or simply curving) is a statistical method of assigning grades designed to yield a pre-determined distribution of grades among the students in a class. The term "curve" refers to the "bell curve", the graphical representation of the probability density of the normal distribution (also called the Gaussian
distribution), but this method of grading does not necessarily make use of any specific frequency distribution such as the bell-shaped normal distribution.
One method of applying a curve uses these three steps: First, numeric scores (or possibly scores on a sufficiently fine-grained ordinal scale) are assigned to the students. The actual values are unimportant as long as the ordering of the scores corresponds to the ordering of how good the students are. In the second step these scores are converted to percentile
s (or some other system of quantile
s). Finally, the percentile values are transformed to grades according to a division of the percentile scale into intervals, where the interval width of each grade indicates the desired relative frequency for that grade.
For example, if there are three grades, A, B and C, where A is reserved for the top 10% of students, B for the next 20%, and C for the remaining 70%, then scores in the percentile interval from 0% to 70% get grade C, scores from 71% to 90% get grade B, and scores from 91% to 100% get grade A.
The grading method can thus be tuned to determine the frequency distribution of the grades in advance, and if the intervals are already fixed at the beginning of a course, then so is the number of students who will receive each grade.
Education
Education in its broadest, general sense is the means through which the aims and habits of a group of people lives on from one generation to the next. Generally, it occurs through any experience that has a formative effect on the way one thinks, feels, or acts...
, grading on a curve (also known as curved grading or simply curving) is a statistical method of assigning grades designed to yield a pre-determined distribution of grades among the students in a class. The term "curve" refers to the "bell curve", the graphical representation of the probability density of the normal distribution (also called the Gaussian
GAUSSIAN
Gaussian is a computational chemistry software program initially released in 1970 by John Pople and his research group at Carnegie-Mellon University as Gaussian 70. It has been continuously updated since then...
distribution), but this method of grading does not necessarily make use of any specific frequency distribution such as the bell-shaped normal distribution.
One method of applying a curve uses these three steps: First, numeric scores (or possibly scores on a sufficiently fine-grained ordinal scale) are assigned to the students. The actual values are unimportant as long as the ordering of the scores corresponds to the ordering of how good the students are. In the second step these scores are converted to percentile
Percentile
In statistics, a percentile is the value of a variable below which a certain percent of observations fall. For example, the 20th percentile is the value below which 20 percent of the observations may be found...
s (or some other system of quantile
Quantile
Quantiles are points taken at regular intervals from the cumulative distribution function of a random variable. Dividing ordered data into q essentially equal-sized data subsets is the motivation for q-quantiles; the quantiles are the data values marking the boundaries between consecutive subsets...
s). Finally, the percentile values are transformed to grades according to a division of the percentile scale into intervals, where the interval width of each grade indicates the desired relative frequency for that grade.
For example, if there are three grades, A, B and C, where A is reserved for the top 10% of students, B for the next 20%, and C for the remaining 70%, then scores in the percentile interval from 0% to 70% get grade C, scores from 71% to 90% get grade B, and scores from 91% to 100% get grade A.
The grading method can thus be tuned to determine the frequency distribution of the grades in advance, and if the intervals are already fixed at the beginning of a course, then so is the number of students who will receive each grade.
See also
- Grade (education)Grade (education)Grades are standardized measurements of varying levels of comprehension within a subject area. Grades can be assigned in letters , as a range , as a number out of a possible total , as descriptors , in percentages, or, as is common in some post-secondary...
- Norm-referenced testNorm-referenced testA norm-referenced test is a type of test, assessment, or evaluation which yields an estimate of the position of the tested individual in a predefined population, with respect to the trait being measured. This estimate is derived from the analysis of test scores and possibly other relevant data...
- List of law school GPA curves
- Normal Distribution
- Bell CurveBell curveBell curve can refer to:* A Gaussian function, a specific kind of function whose graph is a bell-shaped curve* Normal distribution, whose density function is a Gaussian function...