Question

8. The standard deviation of a normal population is 10. You take a sample of 25 items from this population and compute a 95% confidence interval. In order to compute the confidence interval, what will you use. explain your answer

Answer 1

Answer: the z table because the population standard deviation is known

sd = 10
n = 25
se = sd / sqrt(n) = 10 / sqrt(25) = 10 / 5 = 2
95% confidence interval requires two ended alpha to be equal to .05.
.05/2 means alpha os .025 on each end.

z-score required will be plus or minus the z-score that has .025 area to the left of it.

that critical z-score will be plus or minus 1.96
to find the associated raw score, you would need the mean.
unfortunately, the mean is missing from the problem statement.
i think the answer to your question is that you would use the standard error, otherwise known at the standard deviation of the distribution of sample means.
that's the formula i showed you above of se = sd / sqrt(n).