CEVAP:

In some situations, it is not possible to look at all the items in a group for which an index calculation is planned, and some items might have more importance or weight than the others among the group members. When all commodities are not of equal importance, a weight of importance to each commodity might be assigned and an index number is computed then it is called weighted index numbers. The use of a weighted index allows the investigator to give greater importance to some of the items in the group. The importance is highlighted by assigning proper weighting to the values of items in proportion to their relative importance. Information other than the change in price over time can be used and can include such factors as the quantity sold or the quantity consumed for each item.