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 10°C, 20°C, 30°C, and 40°C, using 10 chicks for each RH-Temp combination. The partially completed ANOVA table is as given next.

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.
d. Using dummy variables provide a regression model that can be used to obtain the results in the ANOVA table.
e. What regression model would be appropriate for describing the relationship of RH and Temp to survival time (Y) if the data for the independent variables are to be treated as interval rather than as nominal?

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