percent and weighted results
Message posted by Xavier V-P (via 12.8.181.4) on September 7, 2001 at 9:18 AM (ET)

I collect data on a tool that is divided into 3 sections each having a weight.
each section is based on numper of mets / number of applicables then * their section weight.
Sec-a = 20%
Sec-b = 50%
Sec c = 30%
I know the first calculation is a percent.
My question is
when I take the section percentage results multiplied by their weight then add all three section to obtain a final result is this final result also clasified as a percentage ?

Ex:
a= 8/10=.80*100=80%*.2=16%
B= 29/50=.580*100=58%*.5=29%
c= 15/20=.750*100=75%*.3=22.5%

These three results 16%+29%+22.5%=67.5%

is this 67.5 considered a percentage or a composite score.
why is it not a percentage

Thank you
Xavier

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Re: percent and weighted results
Message posted by Tomi (via 154.32.142.241) on September 8, 2001 at 3:32 AM (ET)

The value you end up with certainly looks like a percentage. It takes values between 0 and 100.

Of course, percentages are only a convenient way of expressing numbers. People are generally happier with the concept of a 75% score than a 0.75 score. So even if what you have is a composite score, then using the notation of percentages is fine.

Big question: will using percentages confuse or clarify? After all, statistics is all about making sense of number. If you give a result of 80%, the impression given will be that the total number of mets/total number of applicables = 0.8

Now because you are weighting, this will not be true. In the example you gave, your weighted score comes out at 67.5%

In fact, the "true" percentage is (8+29+15)/(10+50+20)*100%
=52/80*100%=65%

Clearly there isn't much of a difference, as your weighting (20:50:30) is not very different from the effect of not weighting at all (10:50:20).

Presumably you have good reasons for wanting to emphasise the "a" and "c" measurements, so the 67.5% is "better" because it is being influenced more strongly by the high percentages in "a" and "c".

For clarity, it might be wise in reporting your results to explain your reasons for weighting and give both the unweighted and weighted percentages.