# ROI Major Discussion

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

Using the ROI data set:

1. 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.
1. What are the two possible data values in this column?
2. Given which data value you are looking for, which one is the “success?” Which one is the “failure?”
3. What proportion of the values is the success? This is your p.
4. How many values are there in all? This is your n.
5. What is your z-sub-alpha-over-two value? Did you get it from the chart on page 340? I hope so… 🙂
6. Show how these values have been put into a formula and what the result was.
7. Explain how to get the interval. What did you do with your answer in the previous step?
8. State and interpret the interval.
9. Repeat these steps for the second major.
2. 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.”
1. What is the mean of your data set?
2. What is the standard deviation of your data set?
3. How many numbers are in your data set?
4. What is your z or t sub alpha over two?
5. What formula will you use, and why?
6. Show how you plugged your numbers into the formula and solved.
7. What do you have to do with your answer to #6 to get the interval?
8. 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?