3. The level of dissolved oxygen (DO) in a stream or river is an important indicator of the water's ability to support aquatic life. An average DO level below 5 mg/L puts aquatic life at risk. A researcher wishes to know whether a particular stream is safe. She measures the DO level at 10 randomly chosen locations along a stream. Here are the results in milligrams per liter (mg/L):

5.50, 4.83, 4.40, 5.42, 6.38, 4.01, 4.66, 5.73, 5.55, 5.04

(a) State null and alternative hypotheses relevant to the research question.

(b) Perform a test of the hypotheses from part (a), using a significance level of 10%. You may assume that the distribution of DO levels in the entire stream is approximately normal. Make sure to compute a test statistic and P-value, and make a conclusion in the context of the problem.

(c) Given your conclusion in part (b), which kind of error - Type I or Type II - could you have made? Explain what this mistake would mean in the scientific context of the question.