1 If the standard deviation is unknown and a confidence inte

1. If the standard deviation is unknown and a confidence interval is desired and all assumptions about a distribution being approximately normal is met, which is appropriate the z-distribution or the t-distribution? If the standard deviation is known and a confidence interval is desired and all assumptions about a distribution being approximately normal is met, which is appropriate the z-distribution or the t-distribution?

Solution

1) for unknown std dev, t is appropriate

2) when std dev is known, z is appropriate.