Calcium is essential to tree growth. In​ 1990, the concentration of calcium in precipitation in a certain area was
0.11
milligrams per liter
mgL.
A random sample of 10 precipitation dates in 2018 results in the following data table. Complete parts​ (a) through​ (c) below.
0.079
0.083
0.082
0.261
0.117
0.181
0.132
0.231
0.321
0.091
(a) State the hypotheses for determining if the mean concentration of calcium precipitation has changed since 1990.
(b) Construct a 98​% confidence interval about the sample mean concentration of calcium precipitation.
(c) Does the sample evidence suggest that calcium concentrations have changed since​ 1990?