# Percentile

percentiles50th percentile85th percentile speed95%ileP90percentage pointsweighted percentile
A percentile (or a centile) is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations falls.wikipedia
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### Percentile rank

percentile scorePR
The term percentile and the related term percentile rank are often used in the reporting of scores from norm-referenced tests.
The percentile rank of a score is the percentage of scores in its frequency distribution that are equal to or lower than it. For example, a test score that is greater than 75% of the scores of people taking the test is said to be at the 75th percentile, where 75 is the percentile rank.

### Median

averagesample medianmedian-unbiased estimator
The 25th percentile is also known as the first quartile (Q 1 ), the 50th percentile as the median or second quartile (Q 2 ), and the 75th percentile as the third quartile (Q 3 ).
The median is the 2nd quartile, 5th decile, and 50th percentile.

### Percentage

percent%FG%
A percentile (or a centile) is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations falls.
In British English, percent is usually written as two words (per cent), although percentage and percentile are written as one word.

### Quartile

quartileslower quartilelower and upper quartiles
The 25th percentile is also known as the first quartile (Q 1 ), the 50th percentile as the median or second quartile (Q 2 ), and the 75th percentile as the third quartile (Q 3 ).

### Burstable billing

burstable95e percentile burstable billingburstable rate
When ISPs bill "burstable" internet bandwidth, the 95th or 98th percentile usually cuts off the top 5% or 2% of bandwidth peaks in each month, and then bills at the nearest rate.
The 95th percentile is a widely used mathematical calculation to evaluate the regular and sustained use of a network connection.

### Speed limit

speedingspeed limitsvariable speed limit
The 85th percentile speed of traffic on a road is often used as a guideline in setting speed limits and assessing whether such a limit is too high or low.
The speed limit is commonly set at or below the 85th percentile operating speed (being the speed which no more than 15% of traffic is exceeding) and in the US is frequently set 4 to 8 mph below that speed.

### Weighted median

weights
The 50% weighted percentile is known as the weighted median.
In statistics, a weighted median of a sample is the 50% weighted percentile.

### Standard deviation

standard deviationssample standard deviationsigma
The normal distribution is plotted along an axis scaled to standard deviations, or sigma (\sigma) units.
Percentile

### Quantile

quantilesquintiletertile
In general, percentiles and quartiles are specific types of quantiles.
The 100-quantiles are called percentiles → P

### Decile

deciles
Decile
A decile is one possible form of a quantile; others include the quartile and percentile.

### Order statistic

order statisticsorderedth-smallest of items
Given the order statistics
Percentile

### Summary statistics

summary statisticSummarizationdata summarization
Summary statistics
A simple summary of a dataset is sometimes given by quoting particular order statistics as approximations to selected percentiles of a distribution.

### Statistics

statisticalstatistical analysisstatistician
A percentile (or a centile) is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations falls.

### Norm-referenced test

norm-referencednorm-referenced testsnorm
The term percentile and the related term percentile rank are often used in the reporting of scores from norm-referenced tests.

### Internet service provider

ISPinternet service providersISPs
When ISPs bill "burstable" internet bandwidth, the 95th or 98th percentile usually cuts off the top 5% or 2% of bandwidth peaks in each month, and then bills at the nearest rate.

### Growth chart

child growthgrowth charts
Physicians will often use infant and children's weight and height to assess their growth in comparison to national averages and percentiles which are found in growth charts.

### Normal distribution

normally distributednormalGaussian
In general terms, for very large populations following a normal distribution, percentiles may often be represented by reference to a normal curve plot.

### Infinity

infiniteinfinitely
Mathematically, the normal distribution extends to negative infinity on the left and positive infinity on the right.

### 68–95–99.7 rule

3-sigma68-95-99.7 rulethree sigma rule
This is related to the 68–95–99.7 rule or the three-sigma rule.

### Cumulative distribution function

distribution functionCDFcumulative probability distribution function
In the limit, as the sample size approaches infinity, the 100p th percentile (0

### Glivenko–Cantelli theorem

Glivenko–Cantelli
This can be seen as a consequence of the Glivenko–Cantelli theorem.

### Ranking

rankrankedrankings
The ordinal rank n is calculated using this formula

### Linear interpolation

linearly interpolatedlinearly interpolatinginterpolated
An alternative to rounding used in many applications is to use linear interpolation between adjacent ranks.

### Floor and ceiling functions

floor functionfloorceiling function
where uses the floor function to represent the integral part of positive x, whereas x\%1 uses the mod function to represent its fractional part (the remainder after division by 1). (Note that, though at the endpoint x=N, is undefined, it does not need to be because it is multiplied by x\%1=0.) As we can see, x is the continuous version of the subscript i, linearly interpolating v between adjacent nodes.

### Modulo operation

modulomodmodulus
where uses the floor function to represent the integral part of positive x, whereas x\%1 uses the mod function to represent its fractional part (the remainder after division by 1). (Note that, though at the endpoint x=N, is undefined, it does not need to be because it is multiplied by x\%1=0.) As we can see, x is the continuous version of the subscript i, linearly interpolating v between adjacent nodes.