Chapter 14.1, Problem 25E

Polluting power plants: Power plants can emit levels of pollution that can lower air quality. For this reason, it is important to monitor the levels of pollution they produce. Investigators measured dust emissions, in milligrams per cubic meter, at four power plants. Thirty measurements were taken for each plant. The sample means and standard deviations are presented in the following table.

1. What are the sample sizes $n_1,n_2,n_3,n_4$?
2. What are the sample standard deviations $s_1,s_2,s_3,s_4$?
3. Compute $SSTr$.
4. Compute $SSE$.
5. How many degrees of freedom are there for $SSTr$ ? For $SSE$?
6. Compute $MSTr$ and $MSE$.
7. Compute the value of the test statistic for testing the null hypothesis that the population means are all equal.
8. Can you conclude that the strength differs for different grades of lumber? Use the $\alpha =0.05$ level of significance.