Calcium is essential to tree growth. In 1990, the concentration of calcium in precipitation in Chautauqua, New York, was

0.11 milligram per liter (mg/L).

A random sample of 8 precipitation dates in 2018 results in the following data:

0.087

0.126

0.234

0.065

0.262

0.120

0.108

0.070

A normal probability plot suggests the data could come from a population that is normally distributed. A boxplot does not show any outliers. Does the sample evidence suggest that calcium concentrations have changed since 1990?

Use the a=0.1 level of significance.