Pollution The data in this exercise describe the amount of produced in generating electricity (measured in grams of per kilowatt-hour of electricity generated). Results are from several measurements...

Pollution The data in this exercise describe the amount of

produced in generating electricity (measured in grams of

per kilowatt-hour of electricity generated). Results are from several measurements taken during a year at several plants run by four different electricity-generating utilities using each of three types of fuel: natural gas, coal, and fuel oil.⁴

(a) These data are not from a randomized experiment. What are the implications for modeling the data as a two-way ANOVA?

(b) The measurements were made at different times during the year. What assumption about the twoway ANOVA model becomes questionable as a result?

(c) Are these data balanced? Why or why not?

(d) What does the profile plot indicate? Explain your choice of the variable for the
-axis of the plot.

(e) Perform the two-way ANOVA. What conclusions are implied by the ANOVA summary table, particularly in light of the discovery of major natural gas reserves in the United States?