The level of dissolved oxygen in a river is an importatnt indicator of the water's ability to support aquatic life. You collect water samples at 15 randomly chosen locations along a stream and measure the dissolved oxygen. Here are your results in milligrams per liter:

4.53, 5.04, 3.29, 5.23, 4.13, 5.50, 4.83, 4.40, 5.42, 6.38, 4.01, 4.66, 2.87, 5.73, 5.55

Test to determine if the level of dissolved oxygen in this river is below the 5.4 milligrams per liter that is recommended by the US Fish and Wildlife Service. Carry out an appropriate test of this claim at the =0.05 level.

1.State the hypotheses and identify the claim.

The claim is u is less than 5.4mg per liter of dissolved oxygen in the river that is recommended by the US Fish and Wildlife services.

Ho: U = 5.4

H1: U < 5.4

2.Given an a=0.05, what type of test is used (left tailed, right tailed or two-sided tail) and what is the critical t-value? This is a left tailed, one tail test. df = 15-1 = 14. Critical t value is - 1.761

3.Compute the test value.

(4.771 - 5.4) /(0.94/ Sqrt 15). = -2.591

4.Make the decision.

We reject Ho

5.Summarize the results.

We have sufficient evidence to reject the null hypotheses. T-observed value is less than t-critical value. The level of dissolved oxygen in the river is below the 5.4mg/liter that is recommended by the US Fish and Wild life service.