Question: Can waitresses increase their tips simply by introducing themselves by name when they greet customers? A waitress observes and collects data on 50 people who purchase the same meal at the restaurant. The waitress randomly decides whether to give her name as part of her greeting or not. She gives her name when she greets 25 of the 50 people and doesn’t give her name to another 25 people. Then she keeps track of how much the person gives for a tip at the end of their meal. The distribution is not strongly skewed. Here are the sample results in dollars.

1. Observational study or experiment? Explain . ( 2 pts )
2. What is explanatory variable? Categorical or quantitative? ( 2 pts )
3. What is response variable? Categorical or quantitative? ( 2 pts )
4. State the null and alternative hypotheses in context . ( 2 pts )
5. Calculate the difference in means ( 2 pt s )
6. In this study, is it valid to use the theory-based approach? Explain . ( 2 pts )
7. Calculate the standardized statistic difference in means ( 2 pts )
8. Calculate 95% confidence interval difference in means. Interpret your confidence interval. ( 2 pts )
9. Based on your standardized statistic and 95% confidence interval, what decision you will make about your null hypothesis? Also , interpret your decision into context. ( 2 pts )

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