Math Is Fun Forum
You are not logged in.
- Topics: Active | Unanswered
Pages: 1
#1 2013-04-06 05:38:06
- clueless101
- Member
- Registered: 2013-04-06
- Posts: 5
Weighted averages
How would you find the weighted average of example 14 different countries with different unemployment rates?
Offline
#2 2013-04-06 05:41:05
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Weighted averages
Hi;
Weighted really just means multiplying the data by constants. What are you taking an average of? Do you have some data?
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
Offline
#3 2013-04-06 05:42:48
Re: Weighted averages
Weighted Average of the countries = ((Frequency 1)*(Rate 1) + (Frequency 2)*(Rate 2) + ...)/14
Maybe I need to know more about the problem
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.
Offline
#4 2013-04-06 05:53:21
- clueless101
- Member
- Registered: 2013-04-06
- Posts: 5
Re: Weighted averages
Hey there
The unemployment rate of the 14 countries are the following:
4.0
7.2
6.8
6.6
8.3
7.8
7.8
9.6
6.7
5.1
3.9
7.8
7.8
14.8
Weighted Average is 8.2%
How did they get this 8.2??
Offline
#5 2013-04-06 05:56:23
Re: Weighted averages
just add 'em up and divide by 14
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.
Offline
#6 2013-04-06 06:09:32
- clueless101
- Member
- Registered: 2013-04-06
- Posts: 5
Re: Weighted averages
I have been trying that, but not getting to 8.2
Offline
#7 2013-04-06 06:10:45
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Weighted averages
I do not think you are providing everything. Where are the weights?
You will need them to get 8.2
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
Offline
#8 2013-04-06 06:15:33
- gAr
- Member
- Registered: 2011-01-09
- Posts: 3,482
Re: Weighted averages
Hi clueless101,
There must be another column for weights, by default we take weight to be 1 for each country.
We get 104.2 / 14 = 7.44285714286
"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense" - Buddha?
"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."
Offline
#9 2013-04-06 06:23:34
- clueless101
- Member
- Registered: 2013-04-06
- Posts: 5
Re: Weighted averages
The book only gives me the country names and the unemployment rates
btw thanks guys for your time
Offline
#10 2013-04-06 06:25:55
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Weighted averages
Hi;
That is the entire question? You are sure you have not left anything out?
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
Offline
#11 2013-04-06 06:38:51
- clueless101
- Member
- Registered: 2013-04-06
- Posts: 5
Re: Weighted averages
They do mention that the weights are necessary since the populations of the countries are different. If they were all equal the average would be the sum of all percentages divided by 14.
other than that it's just the country names which I left out
Offline
#12 2013-04-06 06:40:10
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Weighted averages
Maybe they want you to look up the populations of the countries.
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
Offline
#13 2013-04-06 06:44:57
- Bob
- Administrator
- Registered: 2010-06-20
- Posts: 10,190
Re: Weighted averages
Yes that's the weight that is needed.
If you weren't given them, you'll have to look them up.
simple example to show why you have to do this.
Suppose country A has 1000 people and 100 are unemployed. That's 10% unemployed.
Suppose country B has 10 people and 9 are unemployed. That's 90% unemployed.
If you just do (10 + 90)/2 = 50, you've given too much importance to country B
You need to go back to the raw data.
Total population = 1000 + 10 = 1010
Total unemployed = 109.
So true average = 109/1010 x 100 = 10.8%
The answer is properly weighted towards the larger population.
Using the formula {(1000 x 10) + (10 x 90)} / 1010 = 10.8
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob 
Offline
Pages: 1