PDA

View Full Version : confidence int. length known for prop.: how to find margin?



statshelp
04-09-2008, 11:55 AM
If you know the length of a confidence interval for a proportion, How would you find the margin of error?

Please Help!

royhaas
04-09-2008, 12:32 PM
How do you calculate the length of a confidence interval?

statshelp
04-09-2008, 12:47 PM
Max confidence interval - Min confidence interval / 2

royhaas
04-09-2008, 01:05 PM
No, the length is just the difference between the two endpoints of the interval. Now use the formulas for those endpoints and subtract them.

statshelp
04-09-2008, 01:16 PM
Ok so once I find the length, I then divide by 2, to find the margin of error?

royhaas
04-09-2008, 01:18 PM
Just like the calculation implies.

statshelp
04-09-2008, 04:17 PM
Thanks, it just seemed to easy.