For gene has been found to underlie variation in foraging behavior in several insect species. Ben- Shahar et al. (2002) examined whether the gene might influence behavioral differences in the honeybee (Apis mellifera). Worker bees perform tasks in the hive such as brood care (“nursing”) when they are young but switch to foraging for nectar and pollen outside the hive as they age. The authors compared for gene expression in nurse and foraging worker bees in three bee colonies. The results are compiled in the accompanying table. Gene expression is measured in arbitrary units.

a. Draw an interaction plot for these data.

b. Treating COLONY as a blocking variable, write the statement of a linear model to fit to these data. Indicate what each term in the model represents.

c. Write the corresponding null model for a test of whether worker types differ in their mean gene expression.

d. Is worker type a random effect or a fixed effect? Explain.

e. What is the purpose of a blocking variable in experimental design?

Transcribed Image Text:

Worker type Nurse Nurse ForagerForager Nurse Nurse ForagerForager Nurse Nurse ForagerForager Colony 11 11 22 22 33 33 for gene expression 0.990.99 1.931.93 1.001.00 2.362.36 0.240.24 1.961.96