The Orange County Bureau of Weights and Measures reports that the Windsor Bottling Company pours 12 ounces of root beer in its cans. An employee at that company disputes this claim. She takes a random sample of 32 cans and finds average ounces of 11.3 with a standard deviationof .7. Test the null hypothesis at the .01 level of significance. Calculate the confidence interval.
Show your work.

With a confidence interval, do I use the same test statistic formula I do for everything else?

morgaine300

Yes. The test statistic is the z (t) score you get from your sample. That must remain the same regardless.

A level of significance of .01 is the same as being .99 sure (confident) of your results.

The confidence interval is the range of the actual numbers at that point. i.e. not the z-score at that point. But the range of numbers themselves. i.e. the ounces of root beer, from the left side to the right side, at that 99% range.

mean +/- z (sigma/sqrt of n)

The + being the one on the right, and the - being the one on the left. The confidence interval is that range of numbers.

Off to practice those math symbols....

morgaine300

Here, let's see what this looks like:



Except I haven't yet found a symbol for x-bar (mean).