Step by step
The question
Question: what percentile is 58 in 52, 55, 57, 58, 62, 64, 67, 58, 69, 71, 40 and 45?
The percentile of 58 tells what percent of the data is below it.
1 Put them in order
In order, smallest to biggest.
Small green numbers count the positions: 1, 2, 3, and so on.
2 Count below and equal
Below 58: 5 numbers.
That is x.
Equal to 58: 2.
That is y.
x is 5: the numbers below.
y is 2: the numbers equal to 58.
3 Use the rule
The rule: x plus half of y, over n, times 100.
Half of y: the equal ones count half below.
We put the numbers in: x is 5, y is 2, n is 12.
5 plus 1 is 6.
Careful!
Not all of the equal ones: only half of y counts as below.
6 divided by 12, times 100, is 50.
So 58 is at the 50th percentile.
4 Check
Let's check: 5 of 12 are below 58, about 42%.
7 of 12 are up to 58, about 58%.
50 is between them.
So it makes sense!
Let's look back.
First: put them in order.
Then: count below and equal.
Then: use the rule.
Last: check.