Question: how to find the quartile deviation for grouped data?
Answer: Q D = Q 3 − Q 1 2.
The inter-quartile range is given by I Q R = Q 3 − Q 1 .
Q i = ( i ( N ) 4 ) t h value,
where is the total number of observations.
The cumulative frequency just greater than or equal to is . ... 
The cumulative frequency just greater than or equal to is . ... 
The quartile deviation ( ) is.