Good weather and tipping. In Exercise 29.1, you carried out basic ANOVA to compare the mean tipping percents for three experimental conditions.
(a) Find the Tukey simultaneous 95% confidence intervals for all pairwise differences among the three population means.
(b) Explain in simple language what "95% confidence" means for these intervals.
(c) Which pairs of means differ significantly at the overall 5% significance level?
Exercise 29.1:
Good weather and tipping. Exercise 25.35 (text page 650) gives the data for a study on the effect of a waitress's weather prediction on the tipping percent. Carry out data analysis and ANOVA to determine whether there are differences among the mean tipping percents for the three experimental conditions.
Exercise 25.35:
Good weather and tipping. Favorable weather has been shown to be associated with increased tipping. Will just the belief that future weather will be favorable lead to higher tips? The researchers gave 60 index cards to a waitress at an Italian restaurant in New Jersey. Before delivering the bill to each customer, the waitress randomly selected a card and wrote on the bill the same message that was printed on the index card. Twenty of the cards had the message "The weather is supposed to be really good tomorrow. I hope you enjoy the day!" Another 20 cards contained the message "The weather is supposed to be not so good tomorrow. I hope you enjoy the day anyway!" The remaining 20 cards were blank, indicating that the waitress was not supposed to write any message. Choosing a card at random ensured that there was a random assignment of the diners to the three experimental conditions. Here are the tips as a percent of the total bill for the three messages:18
Do the data support the hypothesis that there are differences among the tipping percents for the three experimental conditions? Does a prediction of good weather seem to increase the tip percent? Follow the four-step process in data analysis and ANOVA. Be sure to check the conditions for ANOVA and to include an appropriate graph that compares the tipping percents for the three conditions.