IPSOS opinion and public research company surveyed 2,010 adult Americans and found that, on average, Americans have visited 12 states in the United States. In a survey of 136 statistics students at the school where one of the authors teaches, the average number of states visited was 15.04 and the standard deviation was 9.26. The data were not strongly skewed. 

a. Identify the observational unit for this study. 

b. Identify the variable of interest and whether it is categorical or quantitative. 

c. Clearly the sample is not a randomly selected sample but a convenience sample. With this in mind, would it still be okay to treat the sample as representative of the population of students at the author’s school with regard to “number of states visited”? Explain. 

d. Regardless of your answer to part (c), state the null and the alternative hypotheses in symbols, to test whether the average number of states all students at the author’s school have visited is different from 12. 

e. Use the 2SD approach to find a 95% confidence interval for the average number of states all students at the author’s school have visited.