"Z-test is a statistical hypothesis test that follows a normal distribution while T-test follows a Student's T-distribution" (Ian, 2010). If a study requires a larger sample such as greater than 30 then a Z-test would be a more appropriate test compared to the T-test.
The T-test is better to use for smaller samples. Additionally, if standard deviations (SD) are already known then a Z-test is the better test to use even if it is for a smaller sample. Furthermore a Z-test would be a better test to use if doing a large study on the population whether
the SD is known or not. A T-test is easier to use than a Z-test as a Z-test may need specific conditions in order to render a reliable outcome. Generally a T-test is more common to use due to fact that the t-test has different types of methods which can be used in many ways (Ian, 2010).