Question

2. (1 pt) The following statement is true or false;

When we know the population standard deviation, o, we use a standard normal
distribution (z-score) to calculate the error bound EBM and construct the
confidence interval and when the population standard deviation, o, is unknown,
we use a Student's t distribution (t-score) to calculate the error bound EBM and
construct the confidence interval.
a. true
b. false​

Answer 1

Answer: True

If you know the population standard deviation (sigma), then you use the Z distribution. If sigma is not known, then you use the T distribution.

Side note: Even if sigma is not known, you could use the Z distribution if the sample size n is greater than 30. If n > 30, then the T distribution is approximately about the same as the Z distribution.