For a group of n mutually related items if an index number is found using relative change in the quantity of each item in that group, then the average of all such index numbers is called the quantity index numbers for that group.
Quantity index number is obtained by the following formula:
Quantity index number \(=\frac{\sum (\frac{q_{1i}}{q_{0i}})}{n} \times 100\)
Where, q1i = Current year’s quantity for
ith item (i = 1, 2, 3, …………. n)
q0i = Base year’s quantity fo
ith item (i = 1, 2, 3, ………….. n)
n = Number of items
