For individuals who have not been prescribed Atenolol, the population
systolic blood pressure mean is 165 (µ = 165). The 143 individuals who
take Atenolol have an average systolic blood pressure of 170, with a sample standard deviation of 21. On the basis of these data, can the researcher conclude that the Atenolol significantly lowers systolic blood pressure?

What is the z-value or t-value you obtained (your test statistic)?