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Percentiles Explained

Click through each step to understand the basics.

  1. What Is a Percentile?

    A percentile shows what percentage of a data set falls below a given value β€” being in the 90th percentile means scoring higher than 90% of the entire group.

  2. The Difference Between Percentile and Grade on a Test

    A percentile shows the proportion of test-takers who scored lower than you, while a grade/rank tier shows which of several fixed bands your score falls into β€” two different concepts.

  3. Infant and Child Growth Percentile Charts

    The growth percentile charts used at pediatric checkups show where a child's height and weight fall compared to other children of the same age in months.

  4. The Difference Between Percentile and Simple Rank

    Rank simply shows where you fall among the total number of people, while percentile expresses your relative position as a percentage regardless of the total count, making it easier to compare across groups of different sizes.

  5. The Relationship With Quartiles

    A quartile is a percentile that divides data into four equal parts β€” the 25th percentile is also called the first quartile, and the 75th percentile the third quartile.

  6. The Relationship With the Median

    Since the median splits a data set exactly in half, expressed as a percentile, it's the same as the 50th percentile.

  7. A Common Misunderstanding About Percentiles

    Being in the 90th percentile does not mean scoring 90 out of 100 β€” it only means your relative position compared to others, which is worth keeping in mind.

A Number That Shows Your Relative Position

From practice exam score reports to infant health checkup results, percentiles are widely used to show where you stand within a larger group. They're useful for understanding a relative position that a raw score alone can't reveal.

The Median Is Actually a Special Case of a Percentile

The median, which splits data exactly in half, is in fact a special case of the percentile concept, which is why the two are worth understanding together.

Frequently Asked Questions

Does a 90th percentile mean a score of 90?

No β€” the 90th percentile means scoring higher than 90% of everyone else who took the test, a relative position that's different from the raw score itself.

Is a higher percentile always better?

Generally yes for things like test scores, where higher is better, but depending on what's being measured, a lower percentile can sometimes be more desirable β€” so it's worth checking what the specific measure means.