Question

According to a recent survey, 78% of adults in the world are happy with their air quality. The margin of error was 0.03%. Approximately how many people were surveyed?

Answer 1

What is the first step?

Answer 2

i dont know

Answer 3

What do you think is the first step?

Answer 4

change 78 into a percent or something.

Answer 5

2) Margin of error is NOT 0.03%, it is 3% = 0.03

Answer 6

1)*

Answer 7

78 is already given as a percent...

Look back to your last question for the margin of error formula. I'm assuming this is also a 95% confidence level.

Answer 8

okay whats next?

Answer 9

@SithsAndGiggles Is correct, 78% is already a percentage.

Answer 10

0.03 = 1.96*sqrt [0.78*0.22/n]
n = {1.96/0.03*sqrt [0.78*0.22]}^2 = 733

Do you understand?

Answer 11

yeah but i put 733 in earlier and it was wrong.

Answer 12

What are the selections? Because I got 733.

Answer 13

there's none you just have to fill in the blank

Answer 14

@Jesstho.-. how do we know the margin of error is .03 and not .0003? Maybe they mean .03%.

Answer 15

Oh yes, you're right. @SithsAndGiggles

I think it's the way he put the question, I got sort of confused.

Answer 16

It could still be a typo, but I'd assume it's as written.
\[.0003=1.96\sqrt\frac{.78(1-.78)}n\]and solve for \(n\).

Answer 17

can you write like you did my other question so it can send me straight to the calculator?

Answer 18

I don't think he could put it like that

Answer 19

You mean send you a link to a calculator so I just give you the answer?

Sure, why not.
http://www.wolframalpha.com/input/?i=1.96*Sqrt%5B.78%281-.78%29%2Fn%5D%3D.0003

Answer 20

Oh and @SithsAndGiggles That looks about correct

Answer 21

K! Thanks!

Answer 22

And in case it's as @Jesstho.-. thought: http://www.wolframalpha.com/input/?i=1.96*Sqrt%5B.78%281-.78%29%2Fn%5D%3D.03

Answer 23

Ohh, it's 732 o-o this confused me a lot, great job @SithsAndGiggles