An experiment was conducted to investigate the survival of diplococcus pneumonia bacteria in chick embryos under relative humidities (RH) of 0%, 25%, 50%, and 100% and under temperatures (Temp) of 10C, 20C, 30C, and 40C, using 10 chicks for each RH-Temp combination.9

The partially completed ANOVA table is

as given next.

Source	d.f.	MS
RH		2.010
Temp		7.816
Interaction		1.642
Error		0.775
Total

a. Should the two factors RH and Temp be considered as fixed or random? Explain.

b. Carry out the analysis of variance for both the fixed-effects case and the random- effects case. Do your conclusions differ in the two cases?

c. Write the fixed-effects and the random-effects models that could describe this experiment.