Math Is Fun Forum

llama

Guest

finding an average score

Yes, I'm a math idiot. That's why I'm here.

Here's my question:

I run a weekly poll, and need to know the average score from votes. Some weeks, more people vote than others, but I will find the winner of the contest based on who received the highest average vote. Here's the basic poll (with this week's results):

1.
2.
3.
4.
5.
6.
7.
8.  2 votes
9.
10. 3 votes
11. 4 votes
12. 2 votes
13.
14.
15.

So, there were a total of 11 votes. What number is the average between 1-15? Something like 10.6.

And if there are 15 votes next week, what is the easiest formula for idiots like me to calculate the average score every time, so that I can eventually pick a winner?

Thanks!

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: finding an average score

To find the average, you add together all the numbers and then divide by the amount that there is.

So, in your example, you have the numbers 8, 8, 10, 10, 10, 11, 11, 11, 11, 12 and 12. Adding these makes 114. There are 11 numbers, so divide 114 by this to produce an average of 10.36363636..., or 10.4 when rounded.

If a system like yours gets a lot of votes, there's a trick you can do to make the calculating simpler. Instead of adding up all the votes individually, you can multiply each score by the amount of votes for that score and then add all of those totals.

Using your example again, there were 2 votes for 8, 3 for 10, 4 for 11 and 2 for 12.
So you can do (2x8)+(3x10)+(4x11)+(2x12) = 114.

You don't really need to right now, but if you suddenly start getting lots of votes that technique could be very handy. And as before, you'd divide that total by the number of votes to get the average.

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Why did the vector cross the road?
It wanted to be normal.