Section 6: Statistics Functions 81
Weighted Mean
You can compute the weighted mean of a set of numbers if you know the
corresponding weights of the items in question.
1. Press fCLEAR².
2. Key in the value of the item and press \, then key in its weight and
press _. Key in the second item’s value, press \, key in the second
weight, and press _. Continue until you have entered all the values of the
items and their corresponding weights. The rule for entering the data is
“item \ weight _.”
3. Press gh to calculate the weighted mean of the items.
Example: Suppose that you stop during a vacation drive to purchase gasoline at
four stations as follows: 15 gallons at $1.16 per gallon, 7 gallons at $1.24 per
gallon, 10 gallons at $1.20 per gallon, and 17 gallons at $1.18 per gallon. You
want to find the average cost per gallon of gasoline purchased. If you purchased
the same quantity at each station, you could determine the simple arithmetic
average or mean using the Ö key. But since you know the value of the item
(gasoline) and its corresponding weight (number of gallons purchased), use the
h key to find the weighted mean:
A procedure for calculating the standard deviation and standard error (as well as
the mean) of weighted or grouped data is included in the HP 12C Platinum
Solutions Handbook.
Keystrokes Display
fCLEAR²
0.00
Clears statistics registers.
1.16\15_
1.00
First item and weight.
1.24\7_
2.00
Second item and weight.
1.20\10_
3.00
Third item and weight.
1.18\17_
4.00
Fourth item and weight.
gh
1.19
Weighted mean cost per gallon.
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