A weighted average is. a. a calculation of "average" where each component or item does not have the same weight b. a calculation of "average" where each component or item has an increasing weightc. a calculation of "average" where each component or item has an decreasing weight d. a special case of linear regression

a. a calculation of "average" where each component or item does not have the same weight

Step-by-step explanation:

A weighted average refers to the estimation of a mean or average of two  or more numbers by assigning weight to each of the number because of their different level of importance This is because each number is believed to not contribute equally to the final average, i,e. some numbers or that have higher contribution to the average than the others.

A weighted average is calculated by multiplying each number or data points by the weight that is assigned to it. The all the answers from the multiplications are added and then divided by the number of data points.

For example, let us say we have three set of numbers which are: 4, 9 and 10, and the weights are 4, 2 and 1 respectively, The weighted average can be calculated as follows:

Weighted average = [(4*4) + (9*2) + (10*1)]/3

                               = (16 + 18 + 10)/3

                               = 44/3

                               = 15.67

A weighted average is different the arithmetic mean that does not attach weight to the number. Arithmetic mean can be calculated by simply adding all the data points and divide it by the number of the data points. For the example above, the arithmetic mean is as follows:

Arithmetic mean = (4 + 9 + 10)/3

                               = 23/3

                               = 7.67

The answers show that both are different.

All the best.