calcium is essential to tree growth. in ​, the concentration of calcium in precipitation in​ chautauqua, new​ york, was milligram per liter . a random sample of precipitation dates in results in the following​ data: 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 ​? use the a level of significance. chegg