### CFA Practice Question

There are 985 practice questions for this topic.

### CFA Practice Question

The t-test is used when ______

I. we have large samples and do not know the population variance.
II. we have small samples and know the population variance.
III. we have small samples, do not know the population variance, and the population is normally distributed.
IV. we have large samples and know the population variance.
Correct Answer: I and III

### User Contributed Comments6

User Comment
dnoyelles why not II?
tom1980 if the population variance is known , then we use the z test
chamad I thought we still may use t-test in II and IV but we can not use z-test in I nad III. So my answer was all of them!
cleopatraliao @chamad note that the key word here is population variance.If population variance is known, use z test.
johntan1979 II is assuming normal distribution, which is not stated, hence, t is more appropriate.
Shaan23 First time I've seen Senor John1979 wrong. If we have a small sample regardless of if we know the variance or not AND it is not normal....there's NO test we can do. Cant do Z or T test.