Lessons · Teaching · percentile against percentage
A percentile is not a percentage
A percentage says how much of the paper was right; a percentile says how many others in the comparison group scored at or below this person. Different questions, and the same number means different things.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
What it is for
A parent reads 45th percentile as forty-five percent, which is a fail, and the meeting goes badly for twenty minutes. Being able to say 'she answered 78 percent of the questions correctly, and that puts her ahead of 45 out of every 100 children her age' is the whole difference.
How to think about it
Every time a score appears, ask which of the two it is. If it came off the paper, it is a percentage. If it came from comparing with other people, it is a percentile. Never put both in one sentence without saying which is which.
Worked example
Raw score: 39 of 50A count, with no comparison in it at all.
Percentage = 39 / 50 × 100 = 78%How much of the paper was right.
Percentile 45: 45 out of every 100 scored at or below thisA position in a group, not an amount of anything.
Same person, both numbers trueSeventy-eight percent correct, forty-fifth percentile. Neither of them is wrong.
Your turn
A learner is at the 62nd percentile. Write the line that says how many in a hundred scored at or below them.
62nd percentile: children in 100 scored at or below
Solve one, graded on the server
The trap
Comparing this year's percentile with last year's and calling the difference growth. A percentile is a position in that year's group, and somebody can learn a great deal and still move down it.