A popular pastime has been dropping Men-tos into fresh bottles of cola to generate a plume of fizzing bubbles. Does it matter whether diet soda is used? These data give the brand and type of soda (4 replications for each combination of Coke/Pepsi and diet/regular) and the height in inches of the plume generated.18
(a) Summarize the data in a plot that shows which combination of brand and type produce the largest plume.
(b) Fit and interpret the regression of the height of the plume on the type of soda.
(c) How would the ft of the model change if the regression only included a single dummy variable for diet versus regular?
(d) Do the data satisfy the conditions required for inference in the multiple regression model ft in (c)?
(e) What conclusions are produced by this analysis? Exercises 53 and 54 illustrate some of the consequences of data with unequal group sizes.