Choose ALL the choices that are TRUE for a t-test:

The power of a t-test increases as the standard error increases

Population variance is usually unknown

There is only one t-distribution

The power of a t-test increases as sample size increases

Population mean is usually unknown

There are a family of t-distributions

As sample size decreases, a t-distribution looks more like a Chi-square distribution

As sample size increases, a t-distribution looks more like a Z-distribution