average of averages

When combining sets of data, it is important to consider the size of the sample when calculating an average position or conversion rate. To calculate a weighted average (average of averages), one can add a column calculating the average position by combining the two sets of data, summing the numbers in matching rows, and calculating a new average position = (sum of positions)/(sum of impressions). 1 This approach can also be used to combine calculated metrics such as average, rate, percentage, and conversion rate, as well as to generate a generic approach by breaking down the data into their base metrics, combining duplicate rows, summing the numbers in every column, and recalculating the calculated metrics from the (summed) base metrics. 1 Alternatively, an average can be defined as the sum of the numbers divided by how many numbers are in the list (the arithmetic mean). 2