quartile or third quartile( Q ) has % of the items of the distribution below it and % of the items are above it. Similarly the other two positional measures can be defined. (ii) Deciles: A measure which divides an array into ten equal parts is known as deciles. That is Deciles are the values which divides the series into ten equal parts.
We get nine dividing positions namely D , D ,…, D which are called as deciles. Therefore there are nine deciles. It is to be noted that D is equal to median. (iii) Percentiles: A measure which divides an array into hundred equal parts is known as Percentiles.
That is percentiles are the values which divides the series into hundred equal parts. We get dividing positions P , P ,…, P which are called as percentiles. Therefore there are percentiles. It is to be noted that P is equal to median.
. . Computations for Related positional measure The procedure for computing quartiles, deciles and percentiles are the same as the median. (i) Ungrouped data: Steps: .
Arrange the data either in ascending or descending order of magnitude. . Apply the formula Q = Size of n th l value Q = Size of th b ] g l value D = Size of n th value D = Size of n th l value P = Size of n th l value P = Size of n th l value Q = D = P = Median Example . Find D and D for the following series , , , , , , , , , , Here n = observations are arranged into ascending order , , , , , , , , , , D = size of n th l value D = size of n th l value D = size