Independent t test: Effects of server friendliness on tipping

1. Independent t test: Effects of server friendliness on tipping Aubrey Volger Andrea Firth Todd Carr Philana Kiely

2. Background • Research has focused on gender, number of party, and alcohol consumption in the past but never on the friendliness of a server. There has been very little research on diner/server interactions on tipping. One aspect that has not been studied is the initial contact between server and diner. Our study will show the relationship between friendliness of server and amount of tip left by diner.

3. Experiment Conditions • The effect of a server introducing herself by name on restaurant tipping was investigated. • 42, 2 person dining parties were randomly assigned to either a “name” or “no name” introduction condition. • Use of a buffet brunch reduced contact between server and diners and held bill size constant. • This study indicated that having the server introduce herself by name resulted in a significantly higher tipping rate than when the server did not introduce herself by name. • The findings suggest the importance of initial server-diner interactions.

4. Research Question • Does there appear to be sufficient evidence to conclude with at least 95% confidence that the amount of tip depends on the friendliness of the server?

5. Statistical Hypothesis Ho: μ name tip = μ no name tip H1: μ name tip μ no name tip

6. Decision Rule • Given: • N1 = 21 • N2 = 21 • α=0.05 • df: 36 • If the calculated t is greater than or equal to 2.042, or less than – 2.042, Ho will be rejected.

7. Calculations • Descriptives: • μ name tip = $5.44 • σ name tip = $1.75 • μ no name tip = $3.49 • σ no name tip = $1.13 • The official research results of a two way F test show: • F statistics translate to a t score by taking the square root of f. • F(1,36) = 24.02 t(36) = 4.90 • p < .001 • r2 = 24.02 / (24.02 + 36) = .40

8. Decision • Our calculated value of t(36) = 4.90 is greater than the critical value of 2.042, so we are rejecting the null with at least 95% confidence.

9. Interpretation • Yes, there appears to be sufficient evidence to conclude with at least 95% confidence that the amount of tip depends on server friendliness, t(36) = 4.90, p<.001, r2 =.40. The average percentage of tip for a no name introduction is 15% compared to the average percentage of tip for a name introduction of 23.4%. • With a p value calculated at less than .001, we can conclude with at least 99.9% confidence that there is a difference between average tips left for servers depending on friendliness/introduction.

10. Interpretation cont. • The effect size (r2) for this study of .40 suggests that there is a 40% variance of tip depending on the friendliness of the server. • We can have at least 99.9% confidence that the true mean of name introduction lies within the interval of $3.69-$7.19, and the true mean of no name introduction lies within the interval of $2.36 - $4.62. • The chance for a Type I error is very small because our confidence level is at 99.9%.

11. Future Research • For further research, a study can be done by integrating more variables to see what effects are contributing to the other 60% of variation on tipping. Attractiveness of server Alcohol consumption Number of guests in party Method of payment (Cash vs. Credit Card) Class of the restaurant Gender of server and payer • It is suggested that future research on server identification consider having the maitre d’ give the server’s name to the diners, this would further reduce the likelihood of experimenter effects.