Help with margin of error question?

Question

anonymous · Answer

When you take a random sample of size n from a large population, the sample has a margin of error of approximately ±1/√n. Approximate the margin of error for each sample.

1. In a traffic survey, 42% of the 1287 drivers passing through the checkpoint were traveling more than 100 mi from home.

Can someone show me how to do this?

jim_thompson5910 · Answer

Simply plug n = 1287 (the sample size) into the formula 1/√n to get the margin of error

jim_thompson5910 · Answer

The 42% and the "100 mi from home" facts are irrelevant.

jim_thompson5910 · Answer

oops something weird happened with the symbols

plug n = 1287 into $\Large \frac{1}{\sqrt{n}}$

anonymous · Answer

So, it would be 1/35.9?

jim_thompson5910 · Answer

I wouldn't round til the very end

jim_thompson5910 · Answer

what kind of calculator do you have?

anonymous · Answer

I don't have a scientific one at the moment so I'm using a regular one. 35.87?

jim_thompson5910 · Answer

ok I recommend you use google or wolfram alpha as a scientific calculator if you were to type in "1/sqrt(1287)" without quotes into google, you'd get this https://www.google.com/search?q=1%2Fsqrt(1287)

jim_thompson5910 · Answer

what result do you see?

anonymous · Answer

35.8747822293

jim_thompson5910 · Answer

that's just the square root of 1287

you now have to do 1 over that

jim_thompson5910 · Answer

so that explains why you have to type in   1/sqrt(1287)

anonymous · Answer

Oh! I forgot the divide sign.

anonymous · Answer

Do I turn it into a percent now?

jim_thompson5910 · Answer

yes you do

anonymous · Answer

2.79% margin of error?

jim_thompson5910 · Answer

0.02787 leads to 2.787%

if you rounded, you'd get 2.79%, so I agree

anonymous · Answer

Thank you!

jim_thompson5910 · Answer

you're welcome