I know how percentage work, but percentile? Had to look it up only to forget about it the next day.
In: 4
If you’re in the 95th percentile, then in a room of 100 random people, you’re [better/faster/smarter/bigger/etc] than 95 of them.
It shows quite simply where you would rank in an evenly distributed field.
N% of the population is below the Nth percentile.
For example, the 50th percentile is the median.
Almost everyone (specifically 99 out of every 100) is below the 99th percentile.
Given a collection of members and a given total ordering, a member is in the `n`th percentile if it’s “greater than” or equal to (under the definition given by the total ordering) `n %` of the other members.
So for example, for a given set of requests and their latencies, a request is in the 95th percentile (p95) if its latency is is greater than or equal to 95% of other request latencies. And we say the p95 latency is the cutoff at which that occurs.
Percentile is a way of comparing people to others in a group. If you are in the 80th percentile for whatever it is you are measuring, 20% of the group was above you and 80% below you.
It’s often used for child development, both in terms of physical size (comparing your height/weight to other kids of the same age) and education (comparing test scores to those of others who took the test).
It’s useful when an absolute value is not as informative. Knowing Timmy is 4′ 11″ at 10 years old doesn’t mean much unless you know the average height is closer to 4′ 6″. And a 60% can be a good grade if more than half of test-takers got only a 45%.
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