A study was conducted to determine the effects of individual bathers on the fecal and total coliform bacterial populations in water. The variables of interest were the time since the subject's last bath, the vigor of the subject's activity in the water. and the subject's sex. The experiments were ·performed in a 100-gaUon polyethylene tub using dechlorinated tap water at 38°C. The bacterial contribution of each bather was detem1ined by subtracting the bacterial concentration measured at 15 and 30 minutes from that measured initially.
A replicated 23 factorial design was used "for this experiment. The data obtained are presented below. (Note:· Because the measurement of bacterial populations in water involves a dilution. technique, the experimental errors do not have constant variance. Rather, the variation increases with the value of the mean.) Perform analysis using a logarithmic transformation of the data.
(a) Calculate main and interaction effects on fecal and total coliform populations after 15 and 30 minutes.
(b) Construct ANOVA tables.
(c) Do you think the log transformation is appropriate? Can you discover a better transformation?
