Percentile

Jump to: navigation, search

WikiDoc Resources for Percentile

Articles

Most recent articles on Percentile

Most cited articles on Percentile

Review articles on Percentile

Articles on Percentile in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Percentile

Images of Percentile

Photos of Percentile

Podcasts & MP3s on Percentile

Videos on Percentile

Evidence Based Medicine

Cochrane Collaboration on Percentile

Bandolier on Percentile

TRIP on Percentile

Clinical Trials

Ongoing Trials on Percentile at Clinical Trials.gov

Trial results on Percentile

Clinical Trials on Percentile at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Percentile

NICE Guidance on Percentile

NHS PRODIGY Guidance

FDA on Percentile

CDC on Percentile

Books

Books on Percentile

News

Percentile in the news

Be alerted to news on Percentile

News trends on Percentile

Commentary

Blogs on Percentile

Definitions

Definitions of Percentile

Patient Resources / Community

Patient resources on Percentile

Discussion groups on Percentile

Patient Handouts on Percentile

Directions to Hospitals Treating Percentile

Risk calculators and risk factors for Percentile

Healthcare Provider Resources

Symptoms of Percentile

Causes & Risk Factors for Percentile

Diagnostic studies for Percentile

Treatment of Percentile

Continuing Medical Education (CME)

CME Programs on Percentile

International

Percentile en Espanol

Percentile en Francais

Business

Percentile in the Marketplace

Patents on Percentile

Experimental / Informatics

List of terms related to Percentile


Overview

A percentile is the value of a variable below which a certain percent of observations fall. So the 20th percentile is the value (or score) below which 20 percent of the observations may be found. The term percentile and the related term percentile rank are often used in descriptive statistics as well as in the reporting of scores from norm-referenced tests.

The 25th percentile is also known as the first quartile; the 50th percentile as the median.

There is no standard definition of percentile [1] [2] , however all definitions yield similar results when the number of observations is large. One definition is that the -th percentile of ordered values is obtained by first calculating the rank , rounding to the nearest integer, and taking the value that corresponds to that rank.

An alternative method, used in many applications, is to use linear interpolation between the two nearest ranks instead of rounding. Specifically, if we have values , , ,..., , ranked from least to greatest, define the percentile corresponding to the -th value as In this way, for example, if the percentile corresponding to the third value is Suppose we now want to calculate the value corresponding to a percentile . If or , we take or respectively. Otherwise, we find an integer such that , and take [3] When , the formula gives the median. When is even and , the formula gives the median of the first values.

Linked with the percentile function, there is also a weighted percentile, where the percentage in the total weight is counted instead of the total number. In most spreadsheet applications there is no standard function for a weighted percentile. One method for weighted percentile extends the method described above. Suppose we have positive weights , , ,..., , associated respectively with our sample values. Let be the -th partial sum of these weights. Then the formulas above are generalized by taking and

Relation between percentile, decile and quartile

  • P25 = Q1
  • P50 = D5 = Q2 = median value
  • P75 = Q3
  • P100 = D10 = Q4
  • P10 = D1
  • P20 = D2
  • P30 = D3
  • P40 = D4
  • P60 = D6
  • P70 = D7
  • P80 = D8
  • P90 = D9

Note: One quartile is equivalent to 25 percentile while 1 decile is equal to 10 percentile.

Examples

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. In this way infrequent peaks are ignored, and the customer is charged in a fairer way.

Physicians will often use infant and children's weight and height percentile as a gauge of relative health.

See also

References

http://www.itl.nist.gov/div898/handbook/prc/section2/prc252.htm

  1. Lane, David. "Percentiles". Retrieved 2007-09-15.
  2. Pottel, Hans. "Statistical flaws in Excel" (PDF). Retrieved 2006-03-22.
  3. "Matlab Statistics Toolbox - Percentiles". Retrieved 2006-09-15.

External links


da:Percentil Perzentil it:Percentile nl:Percentiel sv:Percentil ur:صدک


Linked-in.jpg