6. The Whitefly in California The whitefly, which causes defoliation of shrubs and trees and a reduction in salable crop yields, has emerged as a pest in Southern California. A study to determine factors that affect the life cycle of the whitefly was conducted in which whiteflies were placed on two different types of plants at three different temperatures. Each of the six possible treatment combinations was run using five cages, and the total number of eggs laid by the caged females was recorded.

a. What type of experimental design has been used?

b. Do the data provide sufficient evidence to indicate that the effect of temperature on the number of eggs laid is different depending on the type of plant?

c. Plot the treatment means for cotton as a function of temperature. Plot the treatment means for cucumber as a function of temperature. Comment on the similarity or difference in these two plots.

d. Find the mean number of eggs laid on cotton and cucumber based on 15 observations each. Calculate a 95% confidence interval for the difference in the underlying population means.

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Plant 70F Temperature 77F 82F 37 34 46 21 54 32 Cotton 36 40 41 43 42 36 31 16 38 50 59 43 53 53 62 Cucumber 25 31 71 37 69 49 48 51 59 ANOVA Source of Variation SS df MS F P-value F crit Plant 1512.3 1 1512.3 12.293 0.002 4.260 Temperature 487.4667 2 243.733 1.981 0.160 3.403 Interaction 111.2 2 55.6 0.452 0.642 3.403 Within 2952.4 24 123.017 Total 5063.367 29