Water Trace metals found in wells affect the taste of drinking water, and high concentrations can pose a health risk. Researchers measured the concentration of zinc (in milligrams/liter) near the top and the bottom of 10 randomly selected wells in a large region.

The data are provided in the table below.30

(a) Construct and interpret a 95% confidence interval for the mean difference m in the zinc concentrations from these two locations in the wells.

(b) Does your interval in part

(a) give convincing evidence of a difference in zinc concentrations at the top and bottom of wells in the region? Justify your answer.

Well: 1 2 3 4 5 6 7 8 9 10 Bottom: 0.430 0.266 0.567 0.531 0.707 0.716 0.651 0.589 0.469 0.723 Top: 0.415 0.238 0.390 0.410 0.605 0.609 0.632 0.523 0.411 0.612 Difference: 0.015 0.028 0.177 0.121 0.102 0.107 0.019 0.066 0.058 0.111