Data set: Soda
Soda fizz is caused by carbon dioxide that is dissolved into liquid under pressure of up to 1200 pounds per square inch. When the consumer opens the package, pressure is released, the carbon dioxide gas is liberated from the liquid, and gas bubbles rise to the surface. This creates the desired tingling taste. 9 Since soda fizz is caused by the release of a gas, temperature may have an effect on amount of fizz, as gas volume generally increases with increased temperature. Furthermore, since the fizz is caused by gas bubbles being released from the liquid, the tilt of the cup being poured into may also impact the amount of fizz.
Two students, Julie and Daphne, conducted an experiment to test the effects of soda type (Pepsi vs. 7-Up), angle of the cup (cup flat on the table or slightly tipped), and soda temperature (refrigerated at 5° C vs. room temperature at 21° C) on the height of fizz produced when soda was poured out of a can into a cup. For each of the 24 trials, these students poured a can of either Pepsi or 7-Up into a clear cup and measured the peak fizz (in centimeters) produced, using a ruler on the outside of the cup.
a. Create appropriate graphs/charts to check for equal variances and normality. Does it appear that it is appropriate to use ANOVA to analyze these data? Show your work and give concise but appropriate explanations.
b. Conduct a transformation on the data. Instead of using Fizz as the response, use the natural log of Fizz. Using software, conduct an ANOVA for the Soda data. Analyze all main effects, as well as all two-way interactions. Create appropriate graphs that describe the data. Clearly and concisely interpret the results.