Answer: Two-tailed test.
Population mean is the parameter which is tested.
Step-by-step explanation:
Given :
We know that , the alternative hypothesis () indicates kind of the hypothesis test we need to perform whether left-tailed, right-tailed, or two-tailed.
Here, the alternative hypothesis () is two-tailed, so the hypothesis test is a two-tailed test.
Also, the parameter present in the hypothesis is which is a symbol to represent the population mean.
Thus , Population mean is the parameter which is tested.