Your final project must be typewritten (double-spaced, all margins 1", 12 point font), and submitted on plain white, 8½ x 11 paper, stapled, in the following order:
1. Do you think the population of Turkey is more than 80 million?
Yes _____ No _____
2. To the nearest million, estimate the population of Turkey: ______
million.
3. The population of Australia is about 18 million. To the
nearest million, estimate the population of
Canada: _____ million.
and half of the students received a blue form, which contained:
1. Do you think the population of Turkey is more than 10 million?
Yes _____ No _____
2. To the nearest million, estimate the population of Turkey: ______
million.
3. The population of Australia is about 18 million. To the
nearest million, estimate the population of
Canada: ____ million.
So, before estimating the population of Turkey, half of the students saw the number "10 million" and half of the students saw the number "80 million." And, before estimating the population of Canada, all of the students were told the population of "Australia is about 18 million."
The data from this experiment is in:
I:\STAT\250\fall99\lsimon\classdata\popn.mtw
A description of the data in the worksheets follow:| Column name | Description |
|---|---|
| Form | 1 = Blue, 2 = Green |
| MoreThan | Do you think the pop'n is more than? 1 = Yes, 0 = No |
| Turkey | Student's guess of population of Turkey |
| Canada | Student's guess of population of Canada |
| Class | 1 = Fresh, 2 = Soph, 3 = Jun, 4 = Sen, 5 = Other |
| GPA | Student's GPA |
| Geography | Ever taken geography? 0 = No, 1 = Yes |
| EverBeen | Ever been in Canada? 0 = No, 1 = Yes |
Analyze the data for Part I as described below.
1. Using Minitab, create a graph (or graphs) so that you can visually compare the guesses of the population of Turkey for those completing the blue form compared to those completing the green form. Make sure the graph is a type that allows you to identify outliers.
2. Using Minitab, create a graph (or graphs) so that you can visually compare the guesses of the population of Canada for those completing the blue form compared to those completing the green form. Make sure the graph is a type that allows you to identify outliers.
3. Using Minitab, determine the average GPA for those completing the blue form, and determine the average GPA for those completing the green form. Perform a hypothesis test to see if the average GPA of students completing the green form differs from the average GPA of students completing the blue form.
4. Using Minitab, determine the percentage of students having ever taken geography for those completing the blue form, and determine the percentage of students having ever taken geography for those completing the green form. Perform a hypothesis test to see if the percentage of students ever taking geography on the blue form differs from the percentage of students ever taking geography on the green form.
5. Using Minitab, determine the percentage of students having ever been in Canada for those completing the blue form, and determine the percentage of students having ever been in Canada for those completing the green form. Perform a hypothesis test to see if the percentage of students having ever been in Canada on the blue form differs from the percentage of students having ever been in Canada on the green form.
6. Using Minitab, perform a hypothesis test to see if the average guess of the population of Turkey for those completing the blue form is less than the average guess of the population of Turkey for those completing the green form. At the same time, calculate a 95% confidence interval to estimate the true difference in the average guesses of the population of Turkey (for those completing the blue form compared to those completing the green form).
7. Using Minitab, perform a hypothesis test to see if the average guess of the population of Canada for those completing the blue form differs from the average guess of the population of Canada for those completing the green form. At the same time, calculate a 95% confidence interval to estimate the true difference in the average guesses of the population of Canada (for those completing the blue form compared to those completing the green form).
Now, write and submit a report for Part I:
1. We randomly assigned which color form a student received by alternating green and blue forms within a row. (There are better ways to randomize, but this method was the most efficient way of doing it during class time.) The purpose of any randomization is to create groups that are, on average, the same in important characteristics, except for the primary "treatment" of interest. If the randomization did work, we'd expect the groups we are comparing to have roughly the same GPA, the same percentage of students having had a geography course, and the same percentage of students having been in Canada. In analysis items #3-5 above, you analyzed the data to check that indeed the randomization accomplished the goal of "balancing out" the two groups. (There is always a small chance that it didn't balance things out.)
Cut out the output from #3-#5 and paste it to a page. Then summarize
the results in a table like the following:
| Variable | Blue Form | Green Form | p-value |
|---|---|---|---|
| GPA | Average | Average | observed p-value |
| Geography | % | % | observed p-value |
| Been to Canada | % | % | observed p-value |
Write a brief paragraph that summarizes how well our randomization balanced things out. In your summary:
3. Cut out the output from #6 and paste it to a page. Write a brief paragraph that summarizes the results of your hypothesis test for Turkey. In your paragraph:
| Column name | Description |
|---|---|
| Gender | 1 = male, 2 = female |
| Age | 1 = under 21, 2 = At least 21 |
| Class | 1 = lowerclassperson, 2 = upperclassperson |
| Residence | 1 = in PA, 2 = Out of PA |
| Greek | 1 = yes, 0 = no |
| Engaged | 1 = yes, 0 = no |
| Cat | 1 = yes, 0 = no |
| Chew | 1 = yes, 0 = no |
| Cow | 1 = yes, 0 = no |
| Streaked | 1 = yes, 0 = no |
| Save | 1 = spouse, 2 = mother |
| Twins | 1 = one with car, 2 = one without car |
| Burn | 1 = o chem book, 2 = stat 250 notes |
| Procrast | 1 = yes, 0 = no |
| Lottery | 1 = yes, 0 = no |
| Deprived | 1 = yes, 0 = no |
| Deerpens | 1 = yes, 0 = no |
| Passedout | 1 = yes, 0 = no |
| Roommate | 1 = yes, 0 = no |
| Married | 1 = yes, 0 = no |
| Opposite | 1 = yes, 0 = no |
| Body | 1 = yes, 0 = no |
| Fakeid | 1 = yes, 0 = no |
| So | 1 = yes, 0 = no |
| Long | 1 = yes, 0 = no |
| Makebed | 1 = yes, 0 = no |
| Sheets | 1 = yes, 0 = no |
| Nude | 1 = yes, 0 = no |
| Watch | 1 = yes, 0 = no |
| Surgery | 1 = yes, 0 = no |
| Bags | 1 = paper, 2 = plastic |
| Bungee | 1 = yes, 0 = no |
| Meat | 1 = chicken, 2 = beef |
| Fight | 1 = yes, 0 = no |
| Exercise | 1 = yes, 0 = no |
| Run | 1 = yes, 0 = no |
| Horoscope | 1 = yes, 0 = no |
| Tire | 1 = yes, 0 = no |
| Head | 1 = yes, 0 = no |
| Vote | 1 = yes, 0 = no |
| Milk | 1 = yes, 0 = no |
| Adopted | 1 = yes, 0 = no |
| Pornmag | 1 = yes, 0 = no |
| Endworld | 1 = yes, 0 = no |
| Utensil | 1 = pencil, 2 = pen |
| Varsity | 1 = yes, 0 = no |
| Sneakers | Number of pairs of sneakers owned |
| Cards | Number of credit cards in your name |
| Cars | Number of cars you own |
| Drink | Number of days a month you drink alcohol |
| Cry | Number of days you cried in past month |
| Firstalc | Age at which first consumed alcohol |
| Arrested | Number of times been arrested |
| Skipped | Number of Stat 250 classes skipped |
| Coffee | Number of 8-oz cups of coffee daily |
| Urinate | Number of times you urinate in a 24-hour period |
| Study | Number of hours studied for second Stat 250 midterm |
| Santa | Age learned no Santa Claus |
| Jewelry | Number of pieces of jewelry currently wearing |
| Countries | Number of countries visited |
| Games | Number of PSU football games attended this season |
| Books | Number of books read for pleasure this semester |
| Sleephours | Hours of sleep in typical day at Penn State |
| Home | Number of times gone home this semester |
| Cones | Number of Creamery ice cream cones in month |
| Number of times check e-mail in a day | |
| Account | Amount of money in bank account |
| Food | Amount of money typically spent on food weekly |
| Loop | Number of times ride Loop weekly |
| Mirror | Number of times look in mirror daily |
| Bike | Number of times cut off my someone on bike in a day |
| Parktix | Number of parking tickets ever had |
| Breath | How long can hold breath in seconds |
| Waist | Waist size in inches |
| Haircut | Number of times get haircut in semester |
| Cheated | Number of times cheated on a significant other |
| Virgin | 1 = yes, 0 = no |
| Active | 1 = yes, 0 = no |
| Partners | Number of sexual partners in lifetime |
| Sex | Number of times had sex this week |
| Firstsex | Age at first sexual encounter |
It is your job to analyze the data and write a report for Part II as follows:
1. Select one binary variable of interest to you. Using Minitab, calculate a 95% confidence interval for the true percentage of students having the characteristic. Cut out the Minitab output and paste it to your report page. Write a brief paragraph that summarizes the confidence interval and what you have learned. Based on what you know about Penn State students, did you expect the result you got?
2. Select one measurement variable of interest to you. Using Minitab, calculate a 95% confidence interval for the true average of the measurement variable. Cut out the Minitab output and paste it to your report page. Write a brief paragraph that summarizes the confidence interval and what you have learned. Based on what you know about Penn State students, did you expect the result you got?
3. Select a binary grouping variable on the data collection form. Then, select another binary response variable of interest to you. The goal is to see if the groups differ with respect to the binary response variable. That is, you want to compare the percentages having the trait in each of the two groups. Determine your null and alternative hypotheses, and perform a hypothesis test to see if the groups do indeed differ significantly. Cut out your Minitab output and paste it to your report. Write a brief paragraph that summarizes the results of your hypothesis test. In so doing, specify your original hypotheses, state the significance level you used, and specify your decision whether or not to reject. Based on what you know about Penn State students, did you expect the result you got?
4. Select a binary grouping variable on the data collection form. Then, select one measurement response variable of interest to you. The goal is to see if the groups differ with respect to the measurement response variable. That is, you want to compare the averages of the two groups. Determine your null and alternative hypotheses, and perform a hypothesis test to see if the groups do indeed differ significantly. Cut out your Minitab output and paste it to your report. Write a brief paragraph that summarizes the results of your hypothesis test. In so doing, specify your original hypotheses, state the significance level you used, and specify your decision whether or not to reject. Based on what you know about Penn State students, did you expect the result you got?
1. What type of study did the investigators conduct?
2. Why did the authors conduct this study?
3. What are the two treatments being compared in this study? How many patients received each treatment? And how did a patient get assigned to a particular treatment?
4. To which population can the results of this experiment be extended? Be as specific as possible. (In general, study eligibility criteria are used to define the populations.)
5. The authors compared the 2 groups with respect to several outcome measures. Identify one of the binary outcome variables, and identify one of the measurement variables.
6. What is the purpose of Table 1? How did the authors get such similar results in the two groups?
7. Based on the ages reported in Table 1, calculate a 95% confidence interval for the average age for each group. Using the confidence intervals, draw a conclusion about the similarity or difference in the average age in the two groups.
8. What differences are there in the average satisfaction scores at 12 weeks between the two populations? Be as specific and as statistical as possible in your conclusions.
9. Based on the results presented in Table 3, what conclusions can the authors make? Is there evidence that bed rest is an effective treatment for patients with sciatica? Explain.
10. Were the patients successfully blinded to their treatment assignment? Explain.