I'm studying statistics, specifically position measurements.
The problem is that I have seen many ways to calculate the quartile, quintile, percentile, decile, etc.
The main formulas that I have seen to calculate the POSITION of a quartile are:
(n+1)i4 and ni4, where n= number of data, i= number of quartile(1,2,3)
Some websites claim that one formula is to calculate odd data and the other in pairs. However, in many exercises, they use the formula (n + 1) q / 4 for a number of even data and odd numbers of data, without distinction.
What has given me success in the exercises (so far), is to obtain the POSITION of the quartile with the formula (n+1)i4, without distinguishing between odd and even data, and to obtain the VALUE of the quartile I have two options:
a. If the position of the quartile is a decimal, the VALUE will be the average between the two closest integers.
b. If the position of the quartile is an INTEGER, the VALUE will be the data that is in that position.
And I have the same doubt, with the formulas for quintile, decile and percentile.
But my recently exposed methodology has worked well for me, however I come to ask, Is the way I am getting the POSITION and VALUE of the position measurements correct or not correct at all? Thanks in advance.
