Emissions of sulfur dioxide by industry set off chemical changes in the atmosphere that result in "acid rain." The acidity of liquids is measured by pH on a scale of 0 to 14. Distilled water has pH 7.0, and lower pH values indicate acidity. Normal rain is somewhat acidic, so acid rain is sometimes defined as rainfall with a pH below 5.0. Suppose that pH measurements of rainfall on different days in a Canadian forest follow a Normal distribution with standard deviation ? = 0.5. A sample of n days finds that the mean pH is x = 4.8.
1. 4.7 to 4.9
2. 4.51 to 5.09
3. 4.67 to 4.93
4. 4.76 to 4.84
5. 4.63 to 4.97
6. 4.78 to 4.82
A. n = 5
B. n = 15
C. n = 40