# What is the population of interest? What is the sample ?

The CEO of a large electric utility company claims that 83% of his customers are very satisfied with the service they receive. To test this claim, the local newspaper surveyed 100 customers, using simple random sampling. Among the sampled customers, 73 % say they are very satisfied. Based on these findings, is there evidence to suggest that less than 83% of the customers were very satisfied?

Use a 0.05 level of significance. Hint: write the percentages as decimals.

1. What is the population of interest?

What is the sample ?

What variable is being studied here?

4. Describe the parameter of interest in words.

5. What is the value of the statistic for this study?

6. Set up the hypotheses for this study.

7. Given the p-value is 0.01, would you reject or fail to reject the null hypothesis? Why?

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8. Are validity conditions satisfied for using theory-based inference approach? Why or why not?

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9. Compute the standardized statistic for the hypotheses in problem 6 using the theory-based approach. (Hint: I recommend you calculate the SD under the null first)

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10. Based on your standardized statistic you got in 9, what decision do you make? Hint: (Reject/Fail to Reject) the (null/alternative) hypothesis.

Does this agree with your decision you made based on the p value?

11. What does this conclusion mean in context of the problem?聽

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12. Based on your answer in problem 9, what type of error could you have made in this scenario? Write the error in context.

13. Scenario 2:

It is believed that UNL students spend an average of $19 on haircuts. One professor decided to test if her students were spending more than the believed average. The average price of haircuts for the 25 students in her class was $26 with a standard deviation of $20. The distribution of haircuts price for her class was symmetric (not skewed).

1. What variable is studied here? Classify into categorical or quantitative

2. Describe the parameter of interest in words. Give a symbol for it.

(For symbols/notations, you can go to “insert” > “equation” > “greek”)

3. What is the value of the statistic for this study? Give a symbol for it.

4. Write the hypotheses for this study in words.

5. Are validity conditions satisfied for using theory-based inference approach? Why or why not?

6. Compute the theory-based standardized statistic for this study.

7. What conclusion, in context of the study would you make?聽

8. Can we generalize the results of this study to all students at UNL? Why or why not?