Refer to Exercise 6.44. An alternative design of the experiment would involve randomly assigning fumigant F1 to nine of the plots and F2 to the other nine plots, ignoring which fields the plots were from. What are some of the problems that may occur in using the alternative design?
An entomologist is investigating which of two fumigants, F1 or F2, is more effective in controlling parasities in tobacco plants. To compare the fumigants, nine fields of differing soil characteristics, drainage, and amount of wind shield were planted with tobacco. Each field was then divided into two plots of equal area. Fumigant F1 was randomly assigned to one plot in each field and F2 to the other plot. Fifty plants were randomly selected from each field, 25 from each plot, and the numbers of parasites were counted. The data are in the following table.
a. What are the populations of interest?
b. Do the data provide sufficient evidence to indicate a difference in the mean levels of parasites for the two fumigants? Use a Â .10. Report the p-value for the experimental data.
c. Estimate the size of the difference in the mean numbers of parasites between the two fumigants using a 90% confidence interval.