Introduction to SPSS

Transcription

1 Introduction to SPSS Purpose The purpose of this assignment is to introduce you to SPSS, the most commonly used statistical package in the social sciences. You will create a new data file and calculate some basic probabilities. Next you will open an existing data file and calculate the same basic probabilities. Part I: In this part of the assignment, we ll create a new SPSS data file and analyze the data. Creating an SPSS File Open a new SPSS File 1. Double click the SPSS icon on the desktop. If SPSS is not on the desktop, click on the Start button, then click on Applications or All Programs, and then click on SPSS or IBM SPSS. If you cannot find SPSS, click the Start button and then type SPSS into the Search programs and files. 2. A window will pop up and ask you what you would like to do. Click Cancel. Naming Variables 1. SPSS data files have two ways to view the data. Variable View is used for creating the file. Data View is used for entering data. Click on the Variable View tab at the bottom of the window on the left. 2. Click on the first empty cell below Name. 3. Type in Status for the variable. Variable names must be short. Press Enter. 4. Click on the first empty cell in the Label column. Type in Relationship Status for the Status variable. The variable label can be much longer than the variable name. 5. Click on the cell directly below Status. 6. Type in Sex for the next variable. 7. Type in Sex as the label for the Sex variable. 8. For both variables, change the Type to String. To do this, first click in the cell that shows the Type for that variable, and then select the String option. Then click OK. Repeat this process for the other variable. Entering Data in SPSS 1. Click on the Data View tab at the bottom left of the window. In the Data View window, each row represents a participant and each column represents a variable. 2. Click on the first empty cell under the first variable and enter the word Married (the Status for the first participant). You do not need to enter the participant numbers (these are already listed in the far left column as grey numbers). When entering variables, use the arrow or tab keys to move between cells. When you have finished entering data for that participant/row, scroll back and begin with the next participant/row. Enter the following set of data: Participant Status Sex 1 Married Male 2 Single Male 3 Divorced Female 4 Widowed Male 5 Married Female 6 Single Male 7 Single Female 8 Divorced Female 1

2 9 Married Female 10 Single Female 11 Single Male 12 Married Female 13 Married Female 14 Single Male Saving Data in SPSS Initial Save 1. Click on the File menu at the top left of the window. 2. Click on Save As on the drop down menu. 3. From the Look In menu, open a place where you can save your file (such as a flash drive). 4. Type in what you would like to call your file next to File Name. Sometimes, SPSS will suggest a file name, such as Untitled1 [DataSet0]. Change this to something that will be easier to recognize, like Psy 210 Sex and Status Data. 5. Click Save. 6. An output window may appear, telling you that the file has been compressed. To switch back to the Data window, click on the Window menu, and select the Data Editor. Subsequent Saves 1. To save your data, you must first activate the Data window. To do this, click somewhere inside your Data window. Alternatively, click on the Window menu and select the SPSS Data Editor. 2. Click on the File menu at the top left of the window. 3. Click Save on the drop down menu. 4. If you want to save the file under a different name, use Save As. Calculating the Simple Frequencies 1. Click on the Analyze menu. 2. Click on Descriptive Statistics on the drop down menu. 3. Click on Frequencies from the side menu. 4. Choose one of the two variables from the menu on the left (click once to highlight). 5. Click on the arrow button between the two boxes to move that variable to the Variable(s) box on the right. Alternatively, you can drag the variable to the Variable(s) box. 6. Make sure that the box next to Display Frequency Tables has been selected. Click OK. 7. This will bring up an Output window. When you first open the Output window, SPSS will show that it is (Processing ). After a few seconds, the (Processing ) symbol will be replaced by the appropriate output. 8. You can switch back and forth between the Output window and the Data View window by clicking on the Window menu and selecting the window you want, or by using the icons on the bottom of the screen. 9. Check that your output shows a Valid N of 14. If you have a Valid N that is less than 14, then you missed some of the rows when you entered the data. If you have a Valid N that is more than 14, then you may have entered some rows twice or you may have accidently included a blank row. You need to fix your data before you proceed, or else you will get incorrect answers for all of your frequencies. Switch back to Data View, then identify and fix your error. If necessary, you can delete a row by (a) selecting the row, (b) clicking the Edit menu, and clicking Clear. 10. Repeat these steps to calculate the frequencies for the second variable. When you get to step 4, move the first variable back to the left before selecting your new variable: Because you have already calculated descriptive statistics for the first variable; you do not need to calculate them again. 2

3 Calculating Joint Frequencies 1. Click on the Analyze menu. 2. Click on Descriptive Statistics on the drop down menu. 3. Click on Crosstabs from the side menu. 4. Move the variable Status into the Row(s) box. To do this, select the word Status and then click the arrow that is pointing at the Row box. 5. Move the variable Sex into the Column(s) box. 6. Click the Cells button. 7. In the Percentages area, check the Total box. Click Continue. 8. In the Crosstabs box, click OK. Saving Your Output In addition to saving your data, you must also save your output. 1. Click somewhere inside your Output window (the window that popped up after running the Frequencies). 2. Click on the File menu at the top left of the window. 3. Click Save As on the drop down menu. You should name your file Intro to SPSS Last Name Output.spv (replace Last Name with your last name) by typing the name in the File name box. This will make it easy to keep track of your assignments throughout the course. 4. You should save your output file regularly, perhaps after each analysis you do. 5. Do NOT close your output file after each analysis: if you do that, you will end up with many output files (which is very confusing), each of which has to be printed separately. Keep your output file open, so that new analyses are added to the bottom of the file, and save regularly, in case your computer crashes. Computer crashes When a computer crashes, the program you are using may close, or the entire computer may stop responding. When this happens, it is often sufficient to turn the computer off, and then start it up again: use the power button to make sure the computer is completely shut down. You may have to hold the button down for several seconds before the computer turns off. When you are working in a computer lab, turning the computer off and on again might not be enough to fix the problem. If not, I recommend switching computers. Furthermore, sometimes there is a problem with the entire lab (because all the computers in a lab are networked). If switching computers doesn't work, I recommend you move to another computer lab. Computers will crash. So be prepared by saving your files after each change you make. Opening an Output File If you want to open an Output File that you were working on some other day 1. Open SPSS, and close the pop up window that asks what you would like to do. 2. Click on the File menu. 3. Click on Open from the drop-down menu. 4. Click on Output from the side-menu. 5. Select your folder and file. 6. Click Open. Editing Your Output Changing Format to Show 2 Decimals To change the format of the results in the Output window 3

4 1. Double click on the table to open it up for editing. Sometimes SPSS will open the table in a new window, and sometimes it will allow you to edit it in the current window either is fine. If this is the first time you have attempted to edit a table, SPSS will usually open two pop-up windows, one titled Formatting Toolbar and one titled Pivoting Trays. You do not need either of these windows to edit the table and can close them. If they continue to pop up when you double click on tables for editing, you can uncheck them in the View and Pivot menus. 2. Select the cells whose format you want to change. To do this, click the first cell you want to select, then hold down the SHIFT key, and click the last cell you want to select; finally, release the SHIFT key. 3. Click on the Format menu. 4. Click on Cell Properties on the drop down menu. 5. In the Cell Properties window, click on the Format Value menu. 6. To change the number of decimals that are shown, type the number of decimals you want in the box at the bottom of the window, labeled Decimals and click OK. Then click somewhere else on the screen, so that it knows you have finished editing this output. 7. Do this now: In your Frequencies tables for Status and Sex, change the format of the Valid Percent column, so that two decimals are visible for all rows. Repeat these steps to change the number of decimals for the Valid Percent in the Frequency table for your other variable. In the Status * Sex Crosstabulation table, change the % of Total to show two decimals. Deleting Output If you made any mistakes when you were working, you might need to remove a portion of your output. For example, if you do the same analysis twice, you should delete the extra analysis. To delete a portion of your output: 1. Click once on the heading, table, or graph you want to delete. 2. Hit the delete key. To Show More Results Sometimes the computer will not show you all of your results for a particular section. If this happens, to show all your results you should 1. Double click on the section. This will select the section and open it for editing. 2. Click on one of the dots that are on the border, and drag it to resize the window. If no black dots show up, you are seeing everything there is to see. Interpreting Your Output The frequency tables you just created can be used to calculate probabilities. 1. Using the Frequency table for Status, calculate the probability that one of the participants is Married. To insert your answer into your output a. Select the Crosstabulations table by clicking on it once. This way your textbox will show up in the right place. A red arrow will point to the Crosstabulations table. b. Click the Insert menu. c. Selecting New Text from the drop down menu. d. Type your answer to the probability question, with four decimal places. For example, the output shows that the Valid Percent for Divorced is 14.29, if you wanted to show the probability of being divorced, you would write P(divorced) = As you can see, the probability is simply the Valid Percent divided by 100. Using this format, show the probability that a participant is Married. 2. Using the frequency table for Sex, calculate the probability that one of the participants is Female. Insert your answer into the same textbox as the previous probability. 3. Using the Crosstabulation table, calculate the joint probability that one of the participants is a Single Male. Insert your answer into the same textbox as the previous probability. 4

5 4. If you followed these instructions correctly, your textbox should be directly below the Crosstabulations table. If it isn t, don t worry. We will show you how to move it in a minute. Adding a Title to the File In this section, you will add a title to your file, above the word Frequencies 1. Your SPSS Viewer window is divided into two parts: the main part where you see your output, and an outline on the left hand side. If you cannot see the outline, it is minimized. Just drag the divider bar to the right, so that you can see the outline. To add a title, we will use the Outline section. 2. Move your mouse over to the Outline on the left-hand side of the screen and click on the word "Output". When you click on this word, it will highlight this word. Sometimes it will highlight all the sub-headings as well; that s okay. 3. Click on the Insert menu. 4. Click on New Title. The word Title will appear just after the word Output in the outline window. An invisible title box will also be added at the very top of the page in your statistical results, and so all of your results will shift down a little. To show where that title box is, click on the word Title in the Outline window. 5. Now that you can see where the title box is in the main Output window, open it for editing by doubleclicking on it. Type the title Sex and Relationship Status. 6. When you are finished typing, click somewhere else on the page. 7. Now add a second title, above the first one. The title should give your names, the course number and assignment name, and today s date. Use three lines, so this looks organized. 8. Sometimes your title will end up in the wrong part of your output. To fix this, move your mouse over to the Outline window on the left. Then drag the title to where you want it to be. You CANNOT drag stuff around in the main window: You have to use the Outline window. Any time something feels like it is out of order, use the Outline window to move it to its proper place. For example, if the text box with your probabilities is not directly below the Crosstabulations table, put it there now. 9. Save your output. 10. Keep this output file open, so that new output is added to the bottom of this file. Part II: In this part of the assignment, we ll work with an existing SPSS data file. Getting the data file from the Open Science Framework website 1. Using a web browser (e.g., Mozilla Firefox, Google Chrome, or Safari), go to the SPSS Assignments for Introductory Statistics project page on the Open Science Framework website at 2. In the Files section, look under Component: Questionnaire Data for the Questionnaire Data.sav data file. You may have to click the + symbol next to Component: Data or OSF Storage in order to see it. 3. Click on Questionnaire Data.sav. This will allow you to preview the file. 4. To download the data file, click the Download button in the upper right part of the screen. 5. A Save As window will appear. Select the appropriate drive. Check that the file name is specified in the File name box. Then click Save. 6. The file will be downloaded. Once the download is complete, click on the file to open it. Opening a File If you have already downloaded the data file and you just need to open it, here s what you do: 1. In SPSS, click on the File menu at the top left of the window. 2. Click Open on the drop down menu. 3. Click Data from the side menu. 4. Select the appropriate drive from the Look in menu at the top of the screen. 5. Select the appropriate folder from the list of folders in the middle of the screen. 5

6 6. Once you are in the correct folder, double-click on the file name, to select and open it. Alternatively, single click on the file name to select it, and then click Open to open it. Calculating Frequencies 1. Calculate the simple frequencies and joint frequencies for the following two questions: Are you a full-time or part-time student? Are you employed? The results of these analyses will appear at the bottom of your output file, after your analyses for Part I. Make sure you are using the SAME output file for your entire assignment. 2. Round the frequencies to 2 decimal places. 3. Add a title to this section, saying "Student Employment", above the frequencies you just calculated. 4. Calculate the following probabilities and insert your answers into your output using a new textbox: a. The probability that a participant said they were not employed. b. The probability that a participant said they were a full-time student. c. The joint probability that a participant said they were a full-time student who also worked fulltime. 4. This textbox should appear directly AFTER the Crosstabulation table you just created. Move the textbox if necessary. 5. Save your output file. Using Print Preview in SPSS When you have finished the assignment, you should use Print Preview to make sure it looks right. 1. If you want to submit everything in your output file (which you usually do), click on the word Output in the outline window on the left, so that all output is selected. 2. Click File, Print Preview. This shows you what it will look like when you print. 3. To close the Print Preview window and get back to the regular view, click Close. 4. If you see any errors, fix them now. For example, check that your titles are in the right location, and that you don t have any duplicate output. Then use Print Preview again to make sure it looks right. Export Your File to PDF SPSS is an expensive program that you may not have access to on other computers you use. To ensure you are able to read your assignments from any computer, you need to export your file to Adobe PDF. 1. In the left-hand window, click once on Output. This should highlight the entire outline. Click on File at the top and select Export. The Export Window will open. 2. In the Export Window, click on the Selected button 3. Change the Document type to Portable Document Format (*.pdf) 4. Click on the Browse button and select a new location to save your file to (such as your flash drive or your personal folder on the server). 5. Name your file as Intro to SPSS Last Name Output.pdf (replace Last Name with your last name). Click Save. Then click OK to export the PDF. 6. Open your PDF, so you can check it is correct. WHAT YOU SHOULD HAND IN Hand in your output file (in pdf format), which shows the results from both parts of this assignment. 6