of .4th value ≈size of 2nd value = D = size of . th value ≈size of th value = - - Descriptive statistics and probability Example . Calculate the value of Q , Q , D and P from the following data Roll No Marks Marks are arranged in ascending order n = number of observations = Q = Size of n th l value = Size of th l value = Size of nd value = Q = Size of th b ] g l value = Size of th l value = Size of th value = D = Size of th b ] g l value = Size of th l value = Size of . th value = Size of th value = P = Size of th g l value = Size of th value = Hence Q = , Q = , D = and P = (ii) Grouped data (discrete case): Steps: .
Arrange the data in ascending or descending order of magnitude. . Find out cumulative frequencies. .
Apply the formula: Q = Size of N th l value Q = Size of N th b ] g l value Now look at the cumulative frequency ( cf ) column and find that total which is either equal to N l or next higher than that and determine the value of the variable corresponding to this. That gives the value of Q . Similarly Q is determined with reference of N g value of the variable. Example .
Compute Q , D and P from the following data Marks No. of Students Marks Frequency Cumulative Frequency cf N = Table : . Q = Size of N th