Assume you have just accepted a position as chief scientist for a leading agricultural company. Your first assignment is to make a recommendation concerning the best type of grass to grow in the Pacific Northwest and the best fertilizer for it. To provide the database for your recommendation, having just graduated summa cum laude in statistics, you decide to conduct an experiment involving a factorial independent groups design. Since there are three types of grass and two fertilizers under active consideration, the experiment you conduct is 2 _ 3 factorial, where the A variable is the type of fertilizer and the B variable is the type of grass. In your field station, you duplicate the soil and the climate of the Pacific
Northwest. Then you divide the soil into 30 equal areas and randomly set aside 5 for each combination of treatments. Next, you fertilize the areas with the appropriate fertilizer and plant in each area the appropriate grass seed. Thereafter, all areas are treated alike. When the grass has grown sufficiently, you determine the number of grass blades per square inch in each area. Your recommendation is based on this dependent variable. The “denser” the grass is,
the better. The following scores are obtained: Number of Grass Blades
Per Square Inch
Fertilizer
Red
Fescue
Kentucky
Blue
Green
Velvet
Type 1 14 15 15 17 20 19
16 17 12 18 15 22
10 11 25
Type 2 11 7 10 6 15 11
11 8 8 13 18 10
14 12 19
a. What is the null hypotheses for this experiment?
b. Using _ _ 0.05, what are your conclusions? Draw
a graph of the cell means to help you interpret the
results. I/O