Calcium is essential to tree growth because it promotes the formation of wood and maintains cell walls. In 1990, the concentration of calcium in precipitation in a certain area was 0.11 milligrams per liter (mg/L). A random sample of 10 precipitation dates in 2007 results in the following data table:

Question

0.077, 0.071, 0.081, 0.257, 0.116, 0.185, 0.103, 0.223, 0.318, 0.116

a) Construct a 90% confidence interval about the sample mean concentration of calcium precipitation:

(____ , ____) (use ascending order, round to four decimal places)

b) Does the sample evidence suggest that calcium concentrations have changed since 1990?

(Choose one from below)

1) Yes, because the confidence intervalcontains 0.11.

2) No, beacuse the confidence interval does not contain 0.11.

3) Yes, beacuse the confidence interval does not contain 0.11.

4) No, because the confidence interval contains 0.11.

Answer 1

a) (0.1020, 0.1445)

b) 3) Yes, beacuse the confidence interval does not contain 0.11.