EMERGENCY Maths help!

perplex · 5 Nov 2006 at 20:11

Hi. How do you work out confidence intervals? Is it x ± Z*sd ? :confused:

Thanks.

Beansprout · 5 Nov 2006 at 20:23

Why's it an emergency?

Zefan · 5 Nov 2006 at 20:24

Working out the probability of landing on a mattress out of your burning house's window?

cleanbluesky · 5 Nov 2006 at 20:29

Is the maths mob breaking down your door, are they only appeased with correct equations?

Brizzles · 5 Nov 2006 at 20:31

perplex said:
Hi. How do you work out confidence intervals? Is it x ± Z*sd ?

Thanks.

Knowing the distance between toilets, increases my confidence.

perplex · 5 Nov 2006 at 20:32

Thanks.

Beansprout · 5 Nov 2006 at 20:33

perplex said:
Thanks.

You're welcome

None of us know the answer anyway, so we might as well provide amusement

Zefan · 5 Nov 2006 at 20:33

perplex said:
Thanks.

Lol, if we knew I'm sure we'd help.

"andy" · 5 Nov 2006 at 20:37

well id normally use wiki to do my coursework but it wouldnt help if i was a maths guy http://en.wikipedia.org/wiki/Confidence_interval

carvegio · 5 Nov 2006 at 20:47

it depends on the distribution and also what you are working the ci for..

give the full question for a fully reply

Duke · 5 Nov 2006 at 20:55

The answer is 0.999... sorry 1

perplex · 5 Nov 2006 at 21:13

A random sample of 100 electrical leads have a mean length of 1 metre with a standard deviation of 12cm. Find the confidence interval for the true mean length, with:
a) 95% confidence
b) 99% confidence.

Digital Punk · 5 Nov 2006 at 21:17

I'm confident the answers 42.

GlasgowTitan · 5 Nov 2006 at 21:20

Digital Punk said:
I'm confident the answers 42.

The answer to pretty much everything is 42 though, so thats cheating.

Seft · 6 Nov 2006 at 00:38

95% CI is +-1.96*SD/root(n)

Not sure what Z value you need for a 99% CI. Check a table for the normal distribution.

Incidentally, it's emergency stats help...

perplex · 6 Nov 2006 at 08:31

Seft said:
95% CI is +-1.96*SD/root(n)

Not sure what Z value you need for a 99% CI. Check a table for the normal distribution.

Incidentally, it's emergency stats help...

I got 1.96 from notes but I'm not sure how to read the Z table to get it.

MuvverRussia · 6 Nov 2006 at 09:05

Yeah, it's definitely 1.96 for a 99% interval. As for reading tables, it depends on what Normal distribution tables you're using.