Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
Material Type: Lab; Class: Elementary Statistics I; Subject: Statistics; University: Wright State University-Main Campus; Term: Spring 2000;
Typology: Lab Reports
1 / 7
Purpose: To get aquainted with Minitab and Microsoft Word on the Macintosh.
Reading Assignment: Read through Section 2.2.
Problem Description: Set up your diskette for all labs. This includes copying files to your diskette, and setting up a "stationery" (Microsoft) Word document. Also, learn a few Minitab basics, how to copy Minitab output into a (Microsoft) Word document, and how to paginate, save and print Word documents. The data of exercise 2.20 is used.
Copy STT 264 Data Files to Your Diskette : In Lab 1, you initialized a diskette; (If not, do so now, following the directions in Lab 1.) Insert your diskette into the computer, then open it to a window. Next, open (double- click on) the server "Software for ALL users," then the folder "Stats Data"; (A terse way to describe this sequence of steps is: "Software for ALL users -> Stats Data".) Then copy the folder "STT 264 Data" to your diskette (i.e. drag it into your diskette window). On your diskette, open "STT 264 Data" to a window. Then drag each of the files "STT 264 Template" and "Start Minitab.MTB" out of the folder, onto your diskette. Close all of the windows and folders except the one for 'your diskette'.
Set up a stationery Word document: Open the Microsoft Word document file "STT 264 template". If you receive a message,
then open "Macintosh HD", run "Simple Text" and quit. Open ""STT 264 template" again, a document like the follow will open.
Edit the information in the document as appropriate. Specifically, correct the class section number, the names of the members of your lab team, and the name of your instructor. (The current date is used automatically.) Then select "File -> Save As" to obtain a dialog box like the one shown on the next page.
In the dialog box, the name of your diskette should appear in place of "Rowdy Raider, STT 264". Type "STT 264 template" as the document name, and select "Stationery" in the "Save File as Type" box. Then click on the "Save" button.
Finally, close the document. Look in the window for your diskette, to observe that the Word document "STT 264 template" is saved on your diskette. Remember "STT 264 template" is for you to write the Lab report while Minitab is for you to obtain any probabilistic and statistical results. Typically you need to copy and paste these results from Minitab to "STT 264 template".
Starting Minitab : There are several ways to start the Minitab software. It will work out best if you generally use the first method listed below. Still, try the first and third methods now.
1. Starting Minitab from your diskette by opening the file "Start Minitab.MTB": To start Minitab in this way, open `your diskette' to a window if it is not already open, then double-click on "Start Minitab.MTB". Go ahead and start Minitab in this way. (You can speed things up if you click in the "License" window when it appears.) Once Minitab is started, the top window will be an "Untitled Worksheet". Minitab is essentially spreadsheet software but with many nice built-in statistical functions. An important benefit of starting Minitab from a Minitab file on your diskette is that it causes the computer to use your diskette as the default place to save and retrieve files. Now quit Minitab by selecting "File -> Quit". (This is the way you will always close Minitab when finished with it.) 2. Starting Minitab from the server with an empty worksheet : Another way to start the Minitab software is by selecting the software directly from the server. To do this, you would select "Software for ALL users -> Minitab -
Minitab". We may never need to use this method, however. (Don't do this now, or if you did, then select "File -> Quit".)
3. Starting Minitab by opening an existing Minitab Worksheet : Open the Minitab Worksheet "sat.MTW" by selecting "`your diskette' -> STT 264 Data -> sat.MTW". This is the data of textbook Exercise 2.20 (page 39). We will use it to illustrate a few Minitab basics. Use the scroll bar to scroll to the top of the worksheet, in which case it should look like the following.
in the first row mean that there is one observation in the data set of "1975" in the range from 790 to 799. If you go to the data sheet, the number is 794, the 40th observation. The numbers "10" and "011" in the 12th row mean that there are three observations ( 1017, 1002 and 1011) in the data set between 1000 to 1019. The number "8" in the second row means that there is no observation in the data set between 800 and 819.
Menus or commands : Minitab was originally command-driven, meaning that you entered a command to get Minitab to do anything for you. The Macintosh version of Minitab also allows commands to be entered using the menus. You generated the stem-and-leaf plots using the menus. Notice in the Session window that the Minitab command line "MTB > Stem-and-Leaf '1975' '1990'." was generated before the stem-and-leaf plots. "MTB >" is the Minitab prompt, prompting you to enter a command. It is always available at the bottom of the Session window, and you can always enter Minitab commands at the Minitab prompt. To see this, at the Minitab prompt, type "stem c1 c2" then press the return key, and you will obtain the same output as menus. When typing commands, Minitab only uses the first four characters of any command, so "stem" suffices for "stem-and-leaf". As a new user, you will find it easier to use the menus. However, if you notice and learn the command lines generated by Minitab as you use the menus, you can also learn the commands. It is often easier to use the commands, once you know them, than the menus. We will utilize both commands and menus as convenient.
Minitab Windows : Minitab creates many Windows, not all of which are always visible. Use the Window menu to bring up and view each of the Minitab "Session", "Data", "History", and "Info" in turn. The Session window contains all Minitab commands and output generated in the current Minitab Session. Scroll to the top and back to the bottom of it. The Data window contains the minitab worksheet. The History window shows Minitab commands issued during this session (but not output). The Info window provides information on the data in the current worksheet. Whenever Minitab is active, the Windows menu can be used to bring any existing Minitab window to the top of the desktop. This includes for example windows containing high resolution graphs, as we will see later. To reproduce the information about the data set in the Session window, scroll to the bottom of the session window, put the cursor to the right of the Minitab prompt "MTB >", type "info" so the last line looks like "MTB > info", then press the return key. (Do this.)
Creating a new column from existing columns: To evaluate how the SAT scores have changed from 1975 to 1990, we will calculate the paired differences between the scores in 1990 and 1975 and construct a stem-and-leaf plot of the differences. To do this, enter the following commands in the Session window at the Minitab prompt. (You need not enter the "#" characters or any information to the right of them. This is the way to enter comments in Minitab, and comments are not executed -- Minitab ignores them.)
MTB > name c3 'diff' # This gives the name "diff" to column C MTB > let c3 = '1990' - '1975' # This computes the differences MTB > stem c3 # This generates the stem-and-leaf plot.
Look at the stem-plot in the Session window. Also look at the Data window to see the new data generated in column C3 (now named `diff'), and verify that the first few differences were correctly computed.
Generate low resolution histograms : Generate a low resolution histogram for each column of data. To do this, select "Graph -> Histogram...", complete the dialog box as shown below (enter the three variables, and check the High resolution box), then select OK.
Notice that the low resolution graphs are generated in the Session Window. (See what commands were generated in the Session window.)
Generate high resolution histograms on the same scale : Generate high resolution graphs for the data for 1975 and 1990, with both graphs on the same scale. To do this, proceed as for the low resolution histograms, but in the dialog box, just enter the two variables '1975' and '1990' and click in the "Same scale for all variables" box -- leave the "x" in the "High resolution" box. Do this and see what happens. Notice that the two histograms are generated, each in a separate new window. Minitab generates low resolution graphs in the Session window but high resolution graphs in separate windows.
Generate dotplots on the same scale : Dotplots are low resolution plots that are often useful, perhaps because they take up little room, show the data well, and are easily put on the same scale. Select "Graph -> Dotplot...". In the dialog box, select the variables '1975' and '1990', click in the "Same scale for all variables" box, and click "OK". See the resulting plots.
Starting Word for each Lab: For each lab, before you quit Minitab, you will copy your Minitab results into a Word document for printing. Start Word by opening the stationery document "STT 264 template" from your disk (`your disk name' -> STT 264 template). Do this now. Edit the document header information as appropriate, for example to indicate that this is "Lab 2.1," then select "File -> Save". In the resulting dialog box, name the document "Lab 2.1" and save it (as file type "normal"). You are now revising the document "Lab 2.1." (When you revise a stationery document then try to save it, you must rename the document; When you revise a normal document, you can save it any number of times under the same name.) While editing the document, you will be prompted every 5 minutes to save the document, which is wise to do periodically to prevent accidental loss of lots of work.
LAB REPORT: The major portion of this lab is now done. For your lab report, answer the questions given below using the graphs you have generated. Append the Minitab output to your report. Please annotate the Minitab output, boxing and labeling anything cross-referenced in your report. In your report, cross- reference (refer to) the output as appropriate. (Refer to page 4 for further instructions about lab reports.)
(1) Comparing the separate plots for the '1975' and '1990' data, are there any important differences between the two distributions? For example, which data set tends to have larger scores?
(2) You have generated separate stem plots, histograms, and dot plots for the 1975 and 1990 SAT scores. Which of these three types of graphs is most useful for answering question ( 1)? Which is least useful? Explain.
(3) Looking at the plot of differences you generated, how is this plot to be interpreted? Are there any evident changes from 1975 to 1990?
(4) Which do you find more useful for evaluating the change in SAT scores from 1975 to 1990, the separate plots or the plot of differences? Discuss.
Lab 2.1, 12/