statistics confidence interval estimate?

Question

Refer to the list of errors:
-2 -2 0 0 3 2 -10 2 -8 -1 0
1 0 -1 -1 1 0 4 1 1 -1 0
-1 0 4 1 0 2 4 3 6 4 3
2 -2 -2

Assuming that all such errors have a standard deviation of 2.5, construct a 95% confidence interval estimate of the mean of all such errors

i think the mean of the errors= 0.342857143 but i dont know how to do a confidence interval

Answer 1

I get the mean of the sample, Xbar = 0.361, and the standard deviation, σ = 2.5 (given).
Then the 95% confidence is found by:
Xbar ± z(sub α/2)σ/√n; In this case z(sub α/2) = 1.96, because the confidence = (1 - α) = 0.95
So,
0.361 ± 1.96(2.5)/6 gives the 95% confidence limits as -0.456 and 1.178
I hope I've copied the numbers correctly.

Answer 2

The website I listed gives a really good definition and step by step process on how to get the confidence interval.

Good luck