Science Buddies: "Ask an Expert"

I wanna choose the topic : The effect of playing an instrument on your brain (or your intelligence).
And I'm planning to print out an IQ test online and give it to 2 groups of people: one is a non-musicians group and the other is musicians group.
And then I'll check the score according to the web on the Internet that I got the test. Then I'll compute the score and calculate in average to see which group get the higher IQ test.
The purpose of this project is to determine whether playing an instrument is actually advantage for your brain or not.
But I don't know if these procedures are reliable because the data I'm gonna get is basically rely on the web a lot.
So I need some advice on this.
Thanks for your time

This is a great project, but you might find in the end that other hypotheses could explain your results if you find a difference between the two groups. For example, perhaps people with a high IQ are more likely to be inclined to become a musician. Or maybe people with a high IQ have more access to things, including instruments. Or maybe parents are more inclined to buy smart kids instruments... You see the problem.

What you might consider doing is some sort of experimental manipulation. Perhaps you could ask some people to try to play an instrument (I suggest something easy like a recorder) for a half hour or so and have some other people do something else for a half hour, then take the IQ test after that time period. You'd need to randomly determine (maybe flip a coin) which of your subjects were in which tests.

As for relying on online things, be careful to get an accurate IQ test. I've seen plenty of 'free IQ tests' on the web that everyone who takes it scores as a genius because they're trying to sell you something.