Database Reference
In-Depth Information
Figure 15-4. When you turn on the “Weighted average” checkbox, FileMaker adds a second field
list—“Weighted by”—to the window, where you can pick another number field. FileMaker aver-
ages the data in the first field and weights each record's input by the second field.
You use a weighted average when the things you're averaging have an associated quantity.
For example, suppose your database has a record for each product sale. It records which
product was sold, how many were sold, and the unit price. If you want a summary field that
calculates the average sale price, then you probably want to turn on the “Weighted average”
checkbox. Imagine you have these sales figures:
▪ You sold three laptop computers for $2,500 each.
▪ You sold 18 more laptops for $2,200 each.
▪ You sold a single laptop for $2,800.
If you use a simple average, FileMaker tells you the average sale price for laptops is $2,500
($2,500 + $2,800 + $2,200, divided by 3). But that's not exactly right. You sold 18 of those
laptops at just $2,200 each, but it counts only
once
in the calculation. In fact, you really sold
22 laptops in all, at three different prices. To calculate the correct average, you need to take
quantities into consideration. In FileMaker, turn on the “Weighted average” checkbox and
then, in the “Weighted by” list, choose the Quantity field. Now it reports the correct average:
$2,268.18.
Count of
Choose “Count of” to
count
items without totaling them. Since this option doesn't involve
actual math, you can pick
any
field type, not just numbers. FileMaker counts each record in
