What is the formula for calculating the weighted mean?

The formula for calculating the weighted mean is based on the idea of assigning different weights to various values depending on their importance or relevance in a dataset. In the context of the weighted mean, the total assessed value represents one part of the equation, while the total sales price represents another. The weighted mean is found by taking the sum of the values multiplied by their respective weights and then dividing that by the sum of the weights.

In this case, total assessed value divided by total sales price provides a measure that reflects the relationship between the assessed values and the actual market transactions. This approach allows one to obtain a more accurate representation of average values when the transactions or assessments vary significantly in importance or size.

Using the other choices, total sales price divided by the number of transactions yields a simple arithmetic mean rather than a weighted mean. The average of individual assessments also reflects a standard average without considering the differing weights of the individual assessments. Lastly, total economic life divided by effective age pertains to a different context of property valuation rather than the weighted mean calculation. Thus, option A correctly captures the concept and application of the weighted mean formula in this setting.