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.
Answer:
4 T-shirts and 5 long sleeves shirts.
Step-by-step explanation:
T-shirt cost =$10
Long sleeve shirt cost = $15
Total number of shirts = 9
Total number of T-shirts = 4
Cost of 4 T-shirts = 4 × 10 =$ 40
Total number of long sleeve shirt = 5
Cost of 5 long sleeve shirt = 5 × 15 =$ 75
Verification:
75+40 = $115 proved!
