Reconsider the previous exercise.
a. Calculate a 95% confidence interval for the difference in population mean tip amounts between the two experimental treatments (giving name or not).
b. Interpret what this interval means in this context.
c. Is this confidence interval consistent with the test decision from the previous exercise? Explain how you know.
d. Summarize your conclusions from this test. Be sure to comment on issues of causation and generalization as well as significance and confidence.

Data from previous exercise

Can waitresses increase their tips simply by introducing  themselves by name when they greet customers? A waitress collected data on two-person parties that she waited on during Sunday brunch (with a fixed price of $23.21) at a Charley Brown’s restaurant in southern California. For each party the waitress used a random mechanism to determine whether to give her name as part of her greeting or not. Then she kept track of how much the party gave for a tip at the end of their meal.