The purpose of this study is to compare result obtained from three methods of assigning letter grades to students’ achievement.
The conventional and the most popular to assign grades is the Straight Scale method (SS). Statistical approaches which used the Standard Deviation (GC) and
conditional Bayesian method are considered to assign the grades. In the conditional Bayesian model, we assume the data to follow the Normal Mixture distribution. The problem lies in estimating the posterior density of the parameters which is analytically intractable. A solution to this problem is using the Markov Chain Monte Carlo
approach namely Gibbs sampler algorithm. The Straight Scale, Standard Deviation and Conditional Bayesian methods are applied to the examination raw scores of two sets of students. The results showed that Conditional Bayesian out performed the Conventional Methods of assigning grades.