A All values for which z 2807 B All values for which z 257

A: All values for which |z| > 2.807

B: All values for which z > 2.576

C: All values for which z > 2.807

Solution

first of all the samples are less so , t-distribution should be used and even if you are using z statistic then mean and variance should be given whihc is not given here.with t-distribution, its value will be:

from the t-table with 20-1=19 degrees of freedom, a t-value of 2.861 cuts off .005 in two tail.
choice type will be of [A] like |z| > z_{0}.

Let me know about your thoughts on this.