Understanding Percentile Calculation: Confusion and Clarification

[tzx9633]

Homework Statement

I am confused between these 2 videos .

In the first videos , it's same as what i learned in pre-university education course .

When we are calculating kth percentile , the value that we get is whole number , then we need to the use (the value of the current number + value of the next number ) /2

Whereas in the 2nd video , when we are calulating the 20th percentile from 10 number , it's the 2nd number that represent 20% . So , the 20th percentile is the 3rd number , which make sense too .
Because percentile is defined as the percentage of data which is below the value

Homework Equations

The Attempt at a Solution

http://www.dummies.com/education/math/statistics/how-to-calculate-percentiles-in-statistics/

In this link , it's clear that the first video is correct .
I also learned this in pre-u courses . So , i think 2nd video is wrong .

Can someone clarify ?

 

[Ray Vickson]

Homework Statement

I am confused between these 2 videos .

In the first videos , it's same as what i learned in pre-university education course .

When we are calculating kth percentile , the value that we get is whole number , then we need to the use (the value of the current number + value of the next number ) /2

Whereas in the 2nd video , when we are calulating the 20th percentile from 10 number , it's the 2nd number that represent 20% . So , the 20th percentile is the 3rd number , which make sense too .
Because percentile is defined as the percentage of data which is below the value

Homework Equations

The Attempt at a Solution

http://www.dummies.com/education/math/statistics/how-to-calculate-percentiles-in-statistics/

In this link , it's clear that the first video is correct .
I also learned this in pre-u courses . So , i think 2nd video is wrong .

Can someone clarify ?

There are different "definitions" of percentile, and different books use may use different definitions. For example, the Wikipedia article
https://en.wikipedia.org/wiki/Percentile
states that
"There is no standard definition of percentile,[2][3][4] however all definitions yield similar results when the number of observations is very large and the probability distribution is continuous.[5] In the limit, as the sample size approaches infinity, the 100pth percentile (0<p<1) approximates the inverse of the cumulative distribution function (CDF) thus formed, evaluated at p, as p approximates the CDF. "

Which definition of percentile does your textbook (or course notes) use? That is the one you should use also.