# 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.