A Team of Researchers Is Investigating the Effects of Fertilizer

Essay

A team of researchers is investigating the effects of fertilizer on the growth of forest trees. They use an old Christmas tree plantation with pine trees of the same species and age, and divide a section of the plantation into 60 plots. They separate the plots into two groups of 30. They apply high fertilizer levels to the group to the east of the plantation and low fertilizer levels to the western group. They set up the experiment to run for ten years and measure growth of all trees at the end of each year. Discuss the validity of the experimental design, concentrating on the formation of treatment groups and the use of controls. Based on this design, would the researchers be able to draw valid conclusions about the effect of fertilizer on tree growth rates? Why or why not?