Stat 201 – Project 3 – Spring2018
Due Wednesday, April 25, 2018
(1 minute before midnight, submitted to Canvas)
42 TOTAL POINTS
Assignments submitted by 11:59pm on Monday, April 23 will receive +2 bonus points
New Project File: For project 3 you will be using “STAT 201 – Spring 2018 – Project 3.jmp”. This file can be found on the STAT 201 webpage under the “Projects” tab.
Getting Started: In this project, you will explore a subset (i.e., a sample) of some of the data collected from the survey that most Stat 201 students completed this semester. You will be including a substantial amount of output within your write-up. INCLUDE ONLY THE OUTPUT NECESSARY TO ANSWER THE PROJECT QUESTIONS.The data are found in the file “STAT 201 – Spring 2018 – Project 3.jmp”, which is located on the STAT 201 webpage under the “Projects” tab. This file contains 1,049 responses. In real life situations, researchers would use all of the data they have available after conducting a survey. For this project, however, you will get JMP to help you take a random sample from the entire data set so that each student will have different results, and therefore will be turning in a UNIQUE project. The size of the random sample will be 60. When you create your random sample from the original JMP file, JMP creates a new file that will be named “Subset of STAT 201 – Spring 2018 – Project 3”. You should immediately save a copy of this file by clicking the “File” menu and choosing “Save As…”. JMP will prompt you to keep the same name, which is acceptable, or you can rename it to something like “Stat Project3 – My Data”.
Taking Screenshots: Although there are many ways to get JMP graphics into a written presentation, we want you to use the “screen shot” method in all cases. Please see the video at for instructions on how to take selective screen shots on a PC or a Mac. Clearly label what question and part you are answering so your project is graded correctly! See page 5 for an example screenshot for a question.
Tutorials and Write-up: See the JMP tutorials at and for instructions on how to get JMP to perform most tasks. Use page 5 of this project for guidance in which tutorial to look at for each question in the project. In every question that asks you to produce output from JMP, we expect the output you produce to answer the question to be within the write-up. You should put this output immediately after your comments regarding that specific part of the assignment (i.e., not just a series of printouts from JMP at the back of your write-up). You can get help in the Stat 201 Lab with specific questions about the project. You can NOT ask a Stat 201 Lab worker to read your entire project for suggestions on what to change. Your finished work must be submitted within Canvas (see “Assignments”), and must be a Microsoft Word document (.doc or .docx).
JMP and Hodges Library computers: Using JMP installed on your own computer is much simpler than using JMP on a library computer! If you choose to use a computer in the library to do your project, be sure to first read the document “Using JMP in the Library”, found in MyLab under the Project Files tab. Also, you will need to save your project and your random sample subset file to a location you can access later, such as a memory stick. You could also e-mail these files to yourself for later use.
Writing a Good STAT 201 Project Report:Please take note that the last page of the instructions is a page titled “Writing a Good Stat 201 Project Report”. This page contains a series of guidelines for the written part of your report. A portion of your grade (4.8%) is related to following these guidelines.
1.(2 points) The data for this project are found in the file “STAT 201 – Spring2018 – Project 3.jmp”, which is located on the Stat 201 webpageunder the “Projects” tab. From the full database,get JMP to help you take a random sample of size n=60. Save this file. You will be using this random sample data file, and the larger database, to answer the following questions.
As you did in projects 1 and 2, scroll to the bottom of your random sample data file, and take a screen shot of the far-left hand portion of your file that includes the first column and at least the last 10 rows. (See the example on page 5.)
2.In this question, you will be exploring students’ responses to question 25: “Should the United States stop making pennies? (Eliminate the penny)”
a.(2 points) From your random sample data file, consider the variable Q25 - Eliminate the PennyUse Analyze, Distribution to get JMP to display the counts and proportionsof the two possible. Report the sample proportion ()for the proportion of Stat 201 students who answered “Yes” to this question.
[For parts (b) and (c), assume you don’t have access to the full database (i.e., “the population”), but instead only have your sample of n=60. However, assume you do know that the population consists of 1049observations.]
b.(3 points)When calculating a valid confidence interval forp, the true population proportion of Stat 201 students in the Spring2018 survey that answered this question “Yes”, there are three conditionsthat must be met. State each condition in reference to the variable Q25 - Eliminate the Penny. Clearly explain whether or not you think each condition is satisfied. Provide numerical justification where appropriate.
c.(3 points)Regardless of your answers to part (b), get JMP to calculate a 90% confidence interval for p. Report the confidence interval and interpret what this interval means in the context of this problem. (Note: the method JMP uses to calculate confidence intervals for population proportions is slightly different from what you learned in class.)
NOTE - At this point in Question 2, you are going to do something you typically don’t get to do in real life: calculate the true population proportion, p, and compare it to the analysis you just performed.
d.(2 points)From the full database, use Analyze, Distribution to get JMP to display the true population proportion, p:the proportion of Stat 201 students in the Spring2018 survey who answered “Yes” to this question. Report this value in your write-up.
e.(1 point)Does your 90% confidence interval contain the true population proportion p? Provide numerical details.
f.(1 point)Your interval may or may not have contained p, but approximately what percent of your classmates’ 90% confidence intervals do you expect willcontain p?
NOTE-For question 3(h) you will need to make an Excel version of the random sample data set you created earlier. Open your random sample data file in JMP, then PC: File>Save As, select “Excel Workbook” as the File Type. MAC: File>Export>Excel>Next>Export.
3.In this question, you will be exploring students’ answers to question 40: “On an average night, how many hours of sleep during the school year do you usually get?”
[For parts (a) through (i), once again assume you don’t have access to the full database (i.e., “the population”), but instead only have your sample of n=60. However, assume you do know that the population consists of 1049 observations.]
a.(3 points) From your random sample data file, for the variable Q40 - Hours of Sleep Nightly, get JMP to display ahistogram, quantiles and summary statistics for this variable. Your histogram must be in “horizontal layout” and have a count axis.
b.(3 points)We must meet three conditions to perform a hypothesis test and construct a confidence interval for the population average ofnightly hours of sleepforstudents in the Spring2018 survey. Are the three conditions for doing this hypothesis test and calculating a valid confidence interval met in this case? State each condition. Clearly explain whether or not you think each condition is satisfied. Provide numerical justification where appropriate.
c.(2 points)If you Google “how many hours do Americans sleep a night”, you should see a site the top choice. Within this article, it reports that the average hours of night slept for Americans is 6.8 hours. Is there reason to believe that Stat 201 students’ nightly hours of sleep are different than the 2013 average? State the null and alternative hypotheses suggested by this question, using proper mathematical notation. [Although in a report to a non-technical person, you typically would avoid proper mathematical notation, you must use correct mathematical notation here. Hint: on a PC, INSERT tab, Symbol. On a Mac, Insert tab, Advanced Symbols, choose Symbol font.]You can also copy/paste from symbols in this project.
d.(3 points) Regardless of your answers to part (b), perform this hypothesis test using JMP. Display within your report the additional JMP output you generated to do this hypothesis test. Report the p-value for your hypothesis test. Interpret what this p-value means (don’t comment on the magnitude of the p-value, instead tell the reader what this numerical value means).
e.(2 points)Using = 0.05, state your conclusion regarding your null hypothesis. Be sure to state your conclusion in the context of the problem.
f.(3 points)Report your 95% confidence interval for, the population averagehours nightly sleep of Stat 201 students in the Spring2018 survey. Report two decimal place accuracy here. (Hint: the 95% confidence interval is already displayed in the output you generated for part [a].) Interpret what this interval means in the context of this problem.
g.(2 points)Use a calculator tocalculate the margin of error for the confidence interval you reported in part (f). Show or describe the arithmetic you used to calculate this. Use two decimal place accuracy. (HINT: there is an easy and a hard way to do this! Either way is acceptable.)
h.(3 points)From the Excel version of your random sample data file, use Excel to calculate Summary Statistics and the margin of error for a 95% confidence interval (see page 5 of this project for some hints on producing this output). Display within your report the Excel output you generated (it should look similar to the output shown on page 5 of this project). Report the numerical value of the margin of error Excel displayed. Does this reported value from Excel match the margin of error you calculated in part (g)?
i.(2 points) Since you performed a two-sided hypothesis test for using =0.05, and you created a 95% confidence interval for , there should be a direct correspondence between your decision about your null hypothesis and the values within your confidence interval. Explain what it is about your confidence interval that essentially reaches the same conclusion you came to regarding your null hypothesis. Provide numerical details.
j.(1 point) If you used the full database to calculate the average of the population,, you would find that =6.83 hours. Since is NOT 6.83 hours, your null hypothesis in part (c) is in factfalse. You may have rejected or failed to reject the null hypothesis. If you or other students doing this project failed to rejectthe null hypothesis, what “type” of error is this? In general, what are two things a researcher can do to reduce the chance of making this error?
Additional point values:
Project organization and flow (2 points)
Projects should look neat and organized. Use the crop tool in Word if you need to improve screenshots. Your project should read like a report without the prompt of each question.
Use of the guidelines on page 6 (2 points)
The opening paragraph on the project should give a short summary (3-5 sentences) of the analysis they’re about to read. The closing paragraph should summarize interesting findings and discuss any ideas you have regarding further data collection and/or analysis.
JMP Tutorials and Excel Hints Needed for Each Question
Question / Heading / Tutorial / Notes1 / Miscellaneous Topics / Taking a Simple Random Sample / The “Random – sample size” you use will be n=60.
2c, 2d / Inference About a Population Proportion / Confidence Interval and Hypothesis Testing for a Population Proportion / Your data are “unaggregated”, so you will place nothing in the Freq box.
3a / Graphical Display of Quantitative Data / Histogram & Box Plot
3d / T-Tests (Confidence Intervals & Hypothesis Testing) / One-sample t Test
3h / Only Excel for the PC or Excel 2016 for the Mac can perform this work. For both PC and Mac, the “Analysis ToolPak” Add-In must be active:PC: File – Options – Add-Ins – Manage Excel Add-ins – Go… - check Analysis ToolPak – OK. Mac: Tools –Excel Add Ins – check Analysis ToolPak – OK. PC and Mac: See further instructions in the PowerPoint slides, Chapter 18, slides 20-21.
Example Screen Shot for Question 1 / Example Excel Output Question 3(h)
Writing a Good STAT 201 Project Report
Writing a report to your boss about a statistical analysis he has asked you to do is very different than writing a novel, or writing to your Statistics instructor. What does it take to write a good project report? Of course, it’s important to know your audience when you write anything.
Let’s assume you are writing your project report for some busy executives in the company, and they have asked you to answer the questions in the project. They are very intelligent people, but they are not “Statisticians”. Assume that these executives have had some basic statistical education, but perhaps a long time ago. Keep this in mind as you complete your project.
Below are some guidelines for writing an effective project report:
1.The first sentence or two of your report should “orient” the reader. What is this document about? Who is it from? On what date did you complete the analysis?
2.Answer each question on the project instructions using correct sentence structure, spelling and grammar. Sentences should be succinct and clear. You can assume the executives have a copy of the questions they asked.
3.Avoid using "statistical jargon". Explain the results of the analysis in a way that the executives can understand it.
4. As explained in the project instructions, graphics from JMP and/or Excel that address the project question must be imbedded within the document, at the point where the executives need to see them. Don’t make them hunt for the output at the back of your report.
5. Avoid including discussion and/or graphics within the report that have no relevance to the question being addressed.
6.Wrap-up and sign off: some sort of closing sentence regarding how happy you were to answer the executives’ questions, and demonstrate your willingness to do similar work in the near future. The word “Sincerely” or “Regards”, followed by your name is a nice touch at the very end!
rev. 2015-01-22
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