Sewage and industrial pollutants dumped into a body of water can reduce the diss

Question

Sewage and industrial pollutants dumped into a body of water can reduce the dissolved oxygen concentration and adversely affect aquatic species. In one study, weekly readings are taken from the same location in a river over a two-month period.

Week Number / Dissolved O2 (ppm)

1 / 4.9

2 / 5.1

3 / 5.6

4 / 4.3

5 / 4.7

6 / 4.9

7 / 4.5

8 / 5.1

Some scientists think that 5.0 ppm is a dissolved O2 level that is marginal for fish to live. Conduct a statistical test to determine whether the mean dissolved O2 concentration is less than 5.0 ppm at the 95% confidence level.

Is the mean O2 concentration indeed less than 5.0 ppm at the stated confidence level?

Explanation / Answer

Sample Observed Standard Deviation = 0.40156 (use any

Therefore Confidence Interval = (2 x 0.40156)/ 81/2 = 0.28

Hence Range for the true population mean is

(4.8875 - 0.28) to (4.8875 + 0.28)

or 4.61 to 5.16.

So though the observed mean is below 5.0 ppm, the true population mean is not.

Sample Size = 8 Sample Observed Mean = (4.9+5.1+5.6+4.3+4.7+4.9+4.5+5.1)/ 8 = 4.8875

Sample Observed Standard Deviation = 0.40156 (use any

calculator to calculate)

Therefore Confidence Interval = (2 x 0.40156)/ 81/2 = 0.28

Hence Range for the true population mean is

(4.8875 - 0.28) to (4.8875 + 0.28)

or 4.61 to 5.16.

So though the observed mean is below 5.0 ppm, the true population mean is not.

                                                      

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.