Name:
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Please include this on what you hand in!
Graded Assignment 1
Please show your work! Write on one side of your paper. Neatness and whether the papers are stapled may affect your grade.
1. (Duane and Seward) A random sample of rents (to the nearest dollar amount) paid by students living off campus gives the data below. We assume that rents are approximately Normally distributed.
910 820 780 870 860 800 820 810 900 730 920 650
Personalize the data as follows: add the third-to-last digit of your student number to the third-to-last rent above; add the second to last digit to the second-to-last number above, change the last digit the same way.Make sure that your student number is clearly visible on your paper.
Example: Ima Badrisk has student number 123456; so the sample of rents that she uses is below.
910 820 780 870 860 800 820 810 900 734 925 656
Compute the sample standard deviation using the computational formula. (If you don’t know what that means, find out!). Use this sample standard deviation to compute a 90% confidence interval for the mean rent. The Off-Campus Housing Office says that the average amount spent on rents is $870/month. Using the concept of significant difference, does it appear that the office is stating the wrong rent? Why? (This was not an opinion question! If you don’t know what a significant difference is, find out!) Is the mean significantly different from $860?
2. The university wants to publish a document showing its economic impact on the community. If university students rent 965 units, do a confidence interval for the total amount of rent being paid.(See problem 8.50 in the text.)
3. Show how your results in 1) would change if the 12 rentswere a random sample chosen from a population of only 100 rentals.
4. Assume that the population standard deviation is 77 (and that the sample of 12 is taken from a very large population). Find (the 96th percentile of ) using the Normal table and use it and the mean that you found in 1) to compute a 92% confidence interval for the average rent. Does the mean differ significantly from $870 ounces now? From $880? Why?
Extra Credit: (You have to do extra credit now – not after you receive an unacceptable final grade.)
5. a. Use the data above to compute a 90% confidence interval for the population standard deviation.
b. Assume that you got the sample standard deviation that you got above from a sample of 50, repeat a.
c. Fool around with the method for getting a confidence interval for a median and try to come close to a
90% confidence interval for the median.
6. Use the computer labs to access Minitab. Click on the command part of the display (the blank upper sheet). Use editor and ‘enable commands’to start. Check some numbers in the Normal, t, Chi-Squared or F tables using the set of Minitab routines that I have prepared. To use the new set of routines, follow the instructions inAreadoc1. There are several things that you can do. For the Normal distribution use the computer to check the answers to Examples 6.1-6.4 on pp 198-200 in the text. For the t-table pick a number of degrees of freedom and show that for that number of degrees of freedom, the probability above, say, on the t-table is 20%. You can do the same for the F and chi-squared tables in your book of tables. A good answer will explain what you did and contain the command dialog and graphs.
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