For this assignment you will need to reference the data in the ROI Excel spreadheet. Download it here.

Using the ROI data set:

- For each of the 2 majors consider the ‘School Type’ column. Assuming the requirements are met, construct a 90% confidence interval for the proportion of the schools that are ‘Private’. Be sure to interpret your results.
- What are the two possible data values in this column?
- Given which data value you are looking for, which one is the “success?” Which one is the “failure?”
- What proportion of the values is the success? This is your p.
- How many values are there in all? This is your n.
- What is your z-sub-alpha-over-two value? Did you get it from the chart on page 340? I hope so… 🙂
- Show how these values have been put into a formula and what the result was.
- Explain how to get the interval. What did you do with your answer in the previous step?
- State and interpret the interval.
- Repeat these steps for the second major.

- For each of the 2 majors construct a 95% confidence interval for the mean of the column ‘Annual % ROI’. Be sure to interpret your results. This problem is different than the last one because of what is in column D. It’s numbers rather than public/private. For this reason, we can’t use the same formula because there is no “success proportion.”
- What is the mean of your data set?
- What is the standard deviation of your data set?
- How many numbers are in your data set?
- What is your z or t sub alpha over two?
- What formula will you use, and why?
- Show how you plugged your numbers into the formula and solved.
- What do you have to do with your answer to #6 to get the interval?
- State and interpret the interval.

In a highlighted box, make sure to summarize your findings from this week. What does this tell you about ROI?