What is the 2 sided confidence interval for the mean strength of a new structural column? The sample size is 25, the mean is 15,000 pounds, and the sample standard deviation is 200 lbs. Use a confidence level of 95 %.

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- December 8th 2008, 01:39 AMccdelia7Confidence Intervals and Sample Size
What is the 2 sided confidence interval for the mean strength of a new structural column? The sample size is 25, the mean is 15,000 pounds, and the sample standard deviation is 200 lbs. Use a confidence level of 95 %.

- December 8th 2008, 01:49 AMmr fantastic
This is a simple substitution into a standard formula that should be in your textbook or class notes. The formula is here too: 1.3.5.2. Confidence Limits for the Mean.

Where exactly are you stuck? - December 8th 2008, 02:10 AMccdelia7
Honestly, I just think my professor is not clear...I am trying to study for a final, and I cannot figure this problem out. This was an old homework problem, and I don't know how to start. Can you walk me through it?

- December 8th 2008, 02:11 AMccdelia7
I believe, from this data, beta is .05?

- December 8th 2008, 02:34 AMmr fantastic
- December 8th 2008, 02:43 AMccdelia7
Please correct me if I'm wrong...

Lower limit = 14983.5

Upper limit = 15016.5

I substituted what you told me. That's my problem, I dont know where to start on a problem, because there are so many different tests... - December 8th 2008, 02:53 AMccdelia7
I'm sorry, forgot the square root...

Lower Limit = 14917.6

Upper Limit = 15082.6 - December 8th 2008, 03:06 AMmr fantastic