Chapter 11, Problem 15P

In Example 8.1 (page 200) we discussed a research study by Guéguen and Jacob (2012) showing that waitresses received significantly larger tips when they were wearing red T-shirts compared to other colors. The actual study used a repeated-measures design in which waitresses in live different restaurants wore the same T-shirt in six different colors (red, blue, green, yellow, black, and while) on different days during a six-week period. Each waitress recorded the average lip received while wearing red and the average while wearing another color and computed the difference between the two scores. A similar study also found that tips were higher when waitresses wore red, with a mean difference of M_D = 32 cents for each $10 of restaurant bill for a sample of n = 11 waitresses. If the difference scores had s² = 539, are the data sufficient to decide that tips are significantly higher when waitresses wear red? Use a one-failed test with α = .01.