What does 'percentiles' mean?

A common question that students have is: "I got 24 questions right out of 48, why isn’t my percentile 50?"

The answer is that percentage is not always the same as percentile. So what is a percentile score and what does it mean?

The technical definition for percentile is: "The value below which a percentage of data falls" whereas a percentage score indicates the proportion of a test that someone has completed correctly.

For example:

A class of 20 students had the following scores on their most recent test: 75, 77, 78, 78, 80, 81, 81, 82, 83, 84, 84, 84, 85, 87, 87, 88, 88, 88, 89, 90.

The score of 80 has five scores below and equal to it. Since 5/20 = 25%, 80 is the 25th percentile of the class. The score of 87 has 13 scores below it and 2 scores equal to it, so 13 + half of the equal scores = 14/20 = 70%, the scores of 87 are the 70th percentile. The score of 90 would be the 100th percentile score. This is not the only way to calculate percentiles, but is one of the most common.

Simply, a percentile of 72 means that you have performed better than 72% of the MedEntry cohort in that exam/construct and 28% of the MedEntry cohort have performed better than you.

Percentile scores have a variety of uses. A common application of percentiles is in education where percentile scores are used for grading, sometimes referred to as ‘grading on the curve’. This includes tests such as the HPAT or HPAT. Percentiles serve as a basis of comparison for those who took the test.

The ultimate objective of grading curves is to minimize or eliminate any difference in the level of difficulty, real or perceived, ensuring that the students in any given class are assessed relative to their peers.

Updated on: 13/10/2025