This stuff shouldn't be a struggle even for a mathophobe.
Assuming normal distribution.
The formula gives you the margin of error.
The z score that corresponds to a 95% CI is 1.96.
n=144, the number in your sample.
=375, the sample mean.
=20, the standard deviation.
Plug them into your formula:
You can say with 95% confidence that the mean price of all TV's(from the store population) will be between $371.73 and $378.26.
Try it with the 99% CI. See what happens to the interval. Does it widen?. Narrow?.
The z-score that corresponds to 99% is 2.575. Do you have a book with a table to look these up in?.
I think you underestimate your abilities.
THANK YOU FOR YOUR HELP!!!!
Chancer, you didn't happen to delete the problem you posted, did you?
We'd prefer it if you left the problem there. Someone else might also be able to benefit from it. :)