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percentile

  (pər-sĕn'tīl') pronunciation
n.

One of a set of points on a scale arrived at by dividing a group into parts in order of magnitude. For example, a score equal to or greater than 97 percent of those attained on an examination is said to be in the 97th percentile.


 
 

Statistical ranking designation. The pth percentile of a list is the number such that p percent of the elements in the list are less than that number. For example, if a student scores in the 85th percentile on a standardized test, then 85% of those taking the test had lower scores.

 
Dental Dictionary: percentile

n

The number in a frequency distribution below which a certain percentage of fees will fall. For example, the 90th percentile is the number that divides the distribution of fees into the lower 90% and the upper 10%, or that fee level at which 90% of dentists charge that amount or less and 10% charge more.

 
Measures and Units: percentile

statistics A form of quantile.

 

1. one of 100 equal parts of a series of measurements, each group being of equal size, and arranged in order of their magnitude; the 20th percentile is the value in the series below which 20% of the values fall.
2. the dividing points between such groups.

 
Wikipedia: percentile

Definition

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 p-th percentile of N ordered values is obtained by first calculating the rank n = \frac{N}{100}\,p+\frac{1}{2}, 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 N values v1, v2, v3,...,vN , ranked from least to greatest, define the percentile corresponding to the n-th value as p_n=\frac{100}{N}(n-\frac{1}{2}). In this way, for example, if N = 5 the percentile corresponding to the third value is p_3=\frac{100}{5}(3-\frac{1}{2})=50. Suppose we now want to calculate the value v corresponding to a percentile p. If p < p1 or p > pN, we take v = v1 or v = vN respectively. Otherwise, we find an integer k such that p_k\le p \le p_{k+1} , and take v=v_k+\frac{N}{100}(p-p_k)(v_{k+1}-v_k). [3] When p = 50, the formula gives the median. When N is even and p = 25, the formula gives the median of the first \frac{N}{2} 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 w1, w2, w3,...,wN , associated respectively with our N sample values. Let S_n=\sum_{k=1}^{n}w_k be the n-th partial sum of these weights. Then the formulas above are generalized by taking p_n=\frac{100}{S_N}(S_n-\frac{w_n}{2}) and v=v_k+\frac{p-p_k}{p_{k+1}-p_k}(v_{k+1}-v_k).

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 on 2007-09-15.
  2. ^ Pottel, Hans. Statistical flaws in Excel. Retrieved on 2006-03-22.
  3. ^ Matlab Statistics Toolbox - Percentiles. Retrieved on 2006-09-15.

External links


 
Translations: Translations for: Percentile

Dansk (Danish)
n. - percentil

Nederlands (Dutch)
percentiel

Français (French)
n. - pour cent

Deutsch (German)
n. - statistischer Wert, der von 100-n% erreicht wird

Ελληνική (Greek)
n. - τμήμα της κατανομής σε 100 ίσους χώρους, ίδιων γεγονότων

Italiano (Italian)
percentile

Português (Portuguese)
n. - percentil (m)

Русский (Russian)
процентиль

Español (Spanish)
n. - percentil

Svenska (Swedish)
n. - percentil

中文(简体) (Chinese (Simplified))
百分位数之一

中文(繁體) (Chinese (Traditional))
n. - 百分位數之一

한국어 (Korean)
n. - 백분위수

日本語 (Japanese)
n. - 百分位数

العربيه (Arabic)
‏(الاسم) امتئانه : القيمه أو الوحدة الإحصائيه‏

עברית (Hebrew)
n. - ‮מאון (סטטיסטיקה)‬


 
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Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Business Dictionary. Dictionary of Business Terms. Copyright © 2000 by Barron's Educational Series, Inc. All rights reserved.  Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Measures and Units. A Dictionary of Weights, Measures, and Units. Copyright © Donald Fenna 2002, 2004. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Percentile" Read more
Translations. Copyright © 2007, WizCom Technologies Ltd. All rights reserved.  Read more

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