Peacetime test
80,
temporal
90,
End of term
95
The calculation method of subject scores stipulated by the school is:
Usually the test accounts for
20%;
Interim results have been accounted for.
30%;
Final grade accounts for
50%;
Here, the proportion of each achievement is called weight or weight. Then,
weighted average
=
80*20%
+
90*30%
+
95*50%
=
90.5
arithmetic average
=
(80
+
90
+
95)/3
=
88.3
The above example is the case where the weight is known. The following example is the case where the weight is unknown:
Stock a, 1000 shares, price10;
Stock b, 2000 shares, price15;
arithmetic average
=
( 10
+
15)
/
2
=
12.5;
weighted average
=
( 10
x
1000
+
15
x
2000)
/
( 1000
+
2000)
=
13.33
In fact, when the weight of each number is the same, the weighted average is equal to the arithmetic average.
Tip: The Dow Jones Industrial Average is an arithmetic average, and the Standard & Poor's 500 is a weighted average.