Topics in SPSS 12 INDEX 1. Single- Value Frequency Table Categorical Frequency Table Grouped ( Class Limits ) Table

Transcription

1 Topics in SPSS 12 INDEX 1 1. OVERVIEW 2 2. DATA EDITOR 3 3. ORGANIZING DATA 4 Single- Value Frequency Table Categorical Frequency Table Grouped ( Class Limits ) Table 4. DESCRIPTIVE MEASURES 7 Measures of Center Mean, Median, Mode, Measures of Variation Sample Standard deviation, Sample variation Maximum, Minimum, Range, IQR, Skewness and more 5. FIVE NUMBER- SUMMERY ( Minimum, Lower Quartile, Median, Upper Quartile, and Maximum ) 8 6. PLOTTING GRAPHS AND CHARTS 9 Bar Graph Histogram Pie Chart Boxplot Stem-and-Leaf 7. SAVING AND PRINTING OUTPUTS REFERENCES 29 SPSS 12 For Windows / Prepared By M. Zalzali /

2 1. Overview SPSS for Windows provides a powerful statistical analysis and data management system in a graphical environment, using descriptive menus and simple dialog boxes to do most of the work for you. Most tasks can be accomplished simply by pointing and clicking the mouse. In addition to the simple point-and-click interface for statistical analysis, SPSS for Windows provides: Data Editor. A versatile spreadsheet-like system for defining, entering, editing, and displaying data. Viewer. The Viewer makes it easy to browse your results, selectively show and hide output, change the display order results, and move presentation-quality tables and charts between SPSS and other applications. Multidimensional pivot tables. Your results come alive with multidimensional pivot tables. Explore your tables by rearranging rows, columns, and layers. Uncover important findings that can get lost in standard reports. Compare groups easily by splitting your table so that only one group is displayed at a time. High-resolution graphics. High-resolution, full-color pie charts, bar charts, histograms, scatter plots, 3-D graphics, and more are included as standard features in SPSS. Database access. Retrieve information from databases by using the Database Wizard instead of complicated SQL queries. Data transformations. Transformation features help get your data ready for analysis. You can easily subset data, combine categories, add, aggregate, merge, split, and transpose files, and more. Electronic distribution. Send reports to others with the click of a button, or export tables and charts in HTML format for Internet and intranet distribution. Online Help. Detailed tutorials provide a comprehensive overview; context-sensitive Help topics in dialog boxes guide you through specific tasks; pop-up definitions in pivot table results explain statistical terms; the Statistics Coach helps you find the procedures that you need; and Case Studies provide hands-on examples of how to use statistical procedures and interpret the results. Command language. Although most tasks can be accomplished with simple point-and-click gestures, SPSS also provides a powerful command language that allows you to save and automate many common tasks. The command language also provides some functionality not found in the menus and dialog boxes. SPSS 12 for Windows provides several ways to obtain help about how to use SPSS. Every window has a help menu on the menu bar for that window; most dialog boxes have a Help button that links directly to help for that dialog box. Right- clicking ( clicking with the right mouse button ) on most objects (expressions, boxes, and buttons) in a dialog box will result in a context sensitive description of the item that was clicked on. SPSS 12 For Windows / Prepared By M. Zalzali /

3 2. Data Editor The Data Editor provides a convenient, spreadsheet-like method for creating and editing data files. The Data Editor window opens automatically when you start a session. The Data Editor provides two views of your data: Data view. Displays the actual data values or defined value labels. Variable view. Displays variable definition information, including defined variable and value labels, data type (for example, string, date, and numeric), measurement level (nominal, ordinal, or scale), and user-defined missing values. In both views, you can add, change, and delete information contained in the data file. SPSS 12 For Windows / Prepared By M. Zalzali /

4 3. GENERATING FREQUENCY TABLES Objectives: This chapter will focus on how to obtain tables by using SPSS. Such tables are mainly Single- Value Frequency Table Categorical Frequency Table Grouped ( Class Limits ) Table SPSS generates tables that contain Classes, frequencies, percent, valid percent, and cumulative percent Example 1: Generating a single-value table for the following data values Step 1: Click on Variable View. Type Data under name ( or choose any name ), adjust Decimals to 0, Type should be numeric. Step 2: Type the data values in first column SPSS 12 For Windows / Prepared By M. Zalzali /

5 Step 3: From Data View click on Analyze >> Descriptive Statistics >> Frequencies as shown below SPSS will give you the following output Click on the arrow so that data moves to variables Step 4: Click ok SPSS will give you this output Valid Data Cumulative Frequency Percent Valid Percent Percent Total SPSS 12 For Windows / Prepared By M. Zalzali /

6 Example 2: Grouping Categorical Data: Data: D R R R D D I I D D D D D I D D R R R D D R Follow same steps as in example 1. But make changes to Type ( Numeric to String ), and Align to Center ( if you wish ). The width should be as big as the biggest string ( number of characters ). The output will be as follows Categorical Categorical Classes Frequency Percent Valid Percent Cumulative Percent Valid D I R Total Example 3: Grouping data in classes ( limits ) Data: The desired classes are: 50-59, 60-69, 70-79, 80-89, and Step 1: Repeat step 1 in example 1 Step 2: Repeat step 2 in example 1 Step 3: Go to Data >> Sort Cases >> Name of Variable >>A dialog window opens, choose ascending >> OK Step 4: Type the class of each value in the next column and name the variable Class Limits after choosing the Type to be a string. Step 5: From Data View click on Analyze >> Descriptive Statistics >> Frequencies The output from SPSS is Classes Valid Cumulative Frequency Percent Valid Percent Percent Total SPSS 12 For Windows / Prepared By M. Zalzali /

7 4. DESCRIPTIVE MEASURES Objectives: Descriptive measures are numbers calculated from the data that describe certain characteristics of the data file. This chapter will focus on using SPSS to calculate some common descriptive measures. I will concentrate on the following: Example 4: Find Measures of Center Mean, Median, Mode, Measures of Variation Sample Standard deviation, Sample variation Maximum, Minimum, Range, IQR, Skewness and more 1. Number of data N 2. Mean 3. Median 4. Mode 5. Maximum 6. Minimum 7. Range 8. Sample Standard Deviation 9. Sample Variation 10. Skewness 11. IQR 12. Kurtosis 13. Sum of values From the following data Step 1: Enter data in first column, and make sure the Type in Variable View is numeric. Step 2: Click Analyze >> Descriptive Statistics >> Frequencies >>Add Variable Name Step 3: Dialog window opens, click on Statistics and check all the desired variables Step 4: Click Continue >>> OK on the first window The output from SPSS SPSS 12 For Windows / Prepared By M. Zalzali /

8 Data N Statistics Valid 24 Missing 0 Mean Median Mode 78(a) Std. Deviation Variance Skewness Std. Error of Skewness.472 Kurtosis Std. Error of Kurtosis.918 Range 43 Minimum 56 Maximum 99 Sum 1928 Percentiles a Multiple modes exist. The smallest value is shown 5. FIVE NUMBER- SUMMERY ( Minimum, Lower Quartile, Median, Upper Quartile, and Maximum ) Objectives: The five-number-summary for a data set consists of the minimum, maximum, and quartiles, written in increasing order: minimum, lower quartile Q 1 ( P 25 ), Median ( Q 2 ), upper quartile Q 3 ( P 75 ), and maximum. By using SPSS, we can find these values that will be needed to graph boxplots. Example 5: Find the five-number-summary for the following data and Graph the related boxplot Step 1: Enter the data ( Numeric ) Step 2: Click Analayze >> Descriptive Statistics >> Frequencies >> Check the five number-summary that are required >> Continue >> OK SPSS 12 For Windows / Prepared By M. Zalzali /

9 SPSS 12 shows Statistics Data N Valid 24 Missing 0 Median Minimum 56 Maximum 99 Percentiles PLOTTING GRAPHS AND CHARTS Objectives: In this chapter, we will be introduced to graphs and charts. Once we plot them, we can modify the graphs and charts as we please. SPSS supports help for each graph in a friendly manner that we can track the changes and make modifications to the outputs on the spot. We will work on the following: Bar Graph Histogram Pie Chart Boxplot Stem-and-Leaf Example 6: Use the following table to plot a frequency bar graph Grades Letters Frequency ( Number of Students ) A 12 B 15 C 14 D 10 F 3 Step 1: Name first column Grades and assign a string and second column as Frequency and assign a numeric in types Step 2: Click Graphs >> Bar SPSS shows SPSS 12 For Windows / Prepared By M. Zalzali /

10 Choose Simple for a single graph. For two or more choose Clustered. >> Define Step 3: Add Frequency to Bar Represent and Grades to Variables >> OK SPSS 12 will have the following output Value Frequency A B C D F Grades Modifications: Sometimes, we would like to add some flavors to the graph, for instance, the frequency value of each bar, its percentage, or both. Sometimes, we like to change the background of the output and make it more appealing to the subject we are talking about. We should do the following:: SPSS 12 For Windows / Prepared By M. Zalzali /

11 1. Double click on output of the graph, you will receive 2. Right click the graph, you get the following choices The window below is self explanatory. You can make any modification to the graph you wish. If you choose Show Data label. Another dialog opens called properties With the new window ( Properties ) We can change chart size, text, fill & color, and Data Value Labels. For example, click on Data Value Labels. Add to Contents>>> Frequency, Grades, or Percents by clicking them first, then add using the following icon, or we can delete it from contents by using. By using Label Position, click on Custom, we can label the values above, in the middle, or below the bar. Click Apply when you are done. SPSS 12 For Windows / Prepared By M. Zalzali /

12 In this graph, the labels are costumed above the bar and the background is yellow. Example 7: Use the following table to plot a frequency bar graph ( Clustered ) Grades Letters Frequency 1 Frequency 2 A B C D F 3 9 Step 1: Type Grades, Frequency1, and Frequency2 in the Variable View Step 2: Type Grades, Frequency1, and Frequency Data Values in the Data View Step 3: Click Graphs >>> Bar A Bar Graph Chart dialog shows up Click Clustered >>>Values of individual cases >>> Define SPSS 12 For Windows / Prepared By M. Zalzali /

13 Step 4: Move Graphs, Frequency 1, and Frequency 2 to the assigned places as shown below Step 5: Click ok The SPSS output shows 20 Frequency1 Frequency2 15 Value A B C D F Grade Modifications: As we did before, by double clicking the graph, and then, right-clicking, we can add Value labels, etc.as you can see 20 Frequency1 Frequency2 15 Value A B C D F Grade SPSS 12 For Windows / Prepared By M. Zalzali /

14 Example 8: Use the following table to plot a bar graph with relative frequency. Grades Letters Frequency ( Number of Students ) A 12 B 15 C 14 D 10 F 3 Step1: Type in the Variable View as shown below. Step 2: Type the Grades, and Frequency in the Data View as show below Step 3: Click on Transform >>> Compute SPSS 12 For Windows / Prepared By M. Zalzali /

15 Step 4: A dialog window shows Type RelativeF in Target Variable and add the formula in Numeric Expression The values of the relative frequency are executed by SPSS Repeat Steps 1, 2, and 3 in the previous example, but you should use Grades and RelativeF only. SPSS shows in its output SPSS 12 For Windows / Prepared By M. Zalzali /

16 Mean RelativeF A B C D F Grades Histograms SPSS produces a histogram directly from data values. The histogram that is produced doesn t have the correct width and cutpoints or number of classes.. The histogram created in SPSS can be customized. If you use SPSS for the first time, the histogram created will show the midpoints of each class. Such histogram can be modified later when you change some settings. To customize the histogram, select the histogram by double-clicking on it. The Chart Editor window will open and it has its own menu. This can be shown by the next example. Example 9: Construct a histogram from the following data consisting of 5 classes Data ( Histogram ) Step 1: Enter data values in Data View and Name the variable in Variable View. Step 2: Click Graphs >> Histogram. A window dialog opens. Add Histogram Name to Variable >> OK SPSS 12 For Windows / Prepared By M. Zalzali /

17 SPSS output will be 10 8 Frequency Histogram Mean = Std. Dev. = N = 30 This automatic output shows a histogram with 12 classes ( The desired is 5 ). By double-clicking the chart, a Chart Editor Window opens >> Click on X A window opens that shows the properties of the histogram: Our task to modify the classes, cutpoints, ticks & Grids, display a normal curve, change the scale, axis label, etc. SPSS 12 For Windows / Prepared By M. Zalzali /

18 Click on Custom, bullet Number of intervals, and choose 5 >>> Apply SPSS output will show Frequency Histogram Mean = Std. Dev. = N = 30 The new histogram has 5 classes, but the cutpoints don t end at each bar. Now it is our task to have each bar of the histogram has a lower cutpoint and an upper cutpoint. The best way is to figure out the class width, and match it with the starting lower cutpoint. The lower cutpoint should be an integer multiple of the value of the class width. In this example, the class width should be 120, starting point should also be 120. SPSS 12 For Windows / Prepared By M. Zalzali /

19 SPSS output will show Frequency Histogram Mean = Std. Dev. = N = 30 Example 10: Use the following table to plot a pie graph Grades Letters Frequency ( Number of Students ) A 12 B 15 C 14 D 10 F 3 Step 1: Repeat step 1 in example 6. Step 2: Click Graphs >> Pie.. SPSS Shows Click Values of individual cases >> Define Step 3: Add Frequency to Slices Represent and Grades to Variables >> OK SPSS 12 For Windows / Prepared By M. Zalzali /

20 The output by SPSS shows A B C D F Modifications to pie graphs: We can repeat the same steps we did when we modified bar graphs. By Double clicking on the pie, and then right-clicking the mouse, we can add labels, label values, percents, etc Some of these modifications can be noticed by the next pie graphs A B C D F A B C D F F % D 10 A % 22.22% C 14 B % 27.78% Example 11: Graph a boxplot for the following data: Start by entering data values and name the variable. Next click Graphs >> Box Plot >> A Dialogue window opens, click Simple ( for one ) Clustered ( for two or more >>Click Summaries of separate variables >>Define >>Add Variable Name >> OK SPSS 12 gives you SPSS 12 For Windows / Prepared By M. Zalzali /

21 Data Step 5: You can double click on the box plot, and click once on. The box plot will be horizontal. Data Modifications on Boxplots: Double click the boxplot, Click on Y. A dialog window opens Click on Ticks & Grids SPSS 12 For Windows / Prepared By M. Zalzali /

22 Click on Display ticks and insert a number you wish Click Apply, SPSS shows Boxplot SPSS 12 For Windows / Prepared By M. Zalzali /

23 Simple / Clustered Boxplot Summaries of Separate Variables Creates a boxplot summarizing the median, quartiles and extreme values for one or more numeric variables, within clusters defined by a categorical variable. Select at least two variables and move them into the Boxes Represent box. These variables must be numeric. Select a category variable and move it into the Category Axis box. This variable may be numeric, string or long string. You can select a variable and move it into the Label Cases by box. This variable can be numeric or string. If selected, the value labels (or values if no labels are defined) of this variable can be used to label Outliers or extreme cases on the plot. If you do not select a variable to Label Cases by, case numbers can be used to label outliers and extremes. Select Options to specify the treatment of missing values in your data and control whether labels are to be displayed for outliers and extremes. Example 12: Create two boxplots on the same graph by using 1. Simple Boxplot 2. Clustered Boxplot from the following data: Set Simple Boxplots Set Step 1: Enter the data values and Name the variables Box 1 and Box 2 respectively. Step 2: Choose Graphs >>> Boxplot. A dialog opens Click on Simple and Bullet on Summaries of separate variables >>> Define SPSS 12 For Windows / Prepared By M. Zalzali /

24 Step 3: Add Box 1 and Box 2 to Boxes Represent >>> OK SPSS output will show Box1 By double clicking the output, we can make any modifications we desire. Box2 2. Clustered Boxplots Follow the same steps as simple boxplots, but add two variable ( Categorial Axis and Label ), These new variables can be moved later. Make sure you choose Clustered >>> Define Add variables to the new box as follows >>> OK SPSS 12 For Windows / Prepared By M. Zalzali /

25 SPSS output will give you after some modifications Box1 Box CategorialAxis With some extra modifications, the graph will look like Box1 Box2 CategorialAxis SPSS 12 For Windows / Prepared By M. Zalzali /

26 Example 13: Construct a stem-and-leaf diagram from the following data that represent the number of relatives of students in a math class whose section is Step 1: Enter the data in Data View, Name Relatives in the Variable View. Step 2: Click Analyze >> Descriptive Statistics >> Explore Add Relatives to Dependent List Box >> OK Choose Plots and check on Stem-and-leaf box >> Continue Relatives Stem-and-Leaf Plot Frequency Stem & Leaf Stem width: 10 Each leaf: 1 case(s) SPSS 12 For Windows / Prepared By M. Zalzali /

27 7. SAVING AND PRINTING OUTPUTS Often a printed copy of the data file is needed. For example, it is easier to check the accuracy of data from a printed copy than from the computer screen. It is always a good idea to double-check the accuracy of recently entered data. A printed copy may also be required for a report or other document. The data file is printed exactly as it appears in the Data Editor. If you want to print the data values, make sure the data Editor is in Data View. If you want to print the information about the variables, then choose the Variable View tab prior to printing. To obtain a printed copy of a data file, choose File>>>Print and the Print dialog box will open. SPSS has two options that can affect the appearances of the Data Editor. Choosing View>>> Grid Lines from the menu will hide the grid lines. This is a toggle, which means that choosing View>>> Grid Lines again will make the grid line reappear. If the data file has value labels, then choosing View >> Value Labels toggles between displaying data values and displaying value labels. After tying in a new data file or editing an old data file, the contents of the Data Editor should be saved. This preserves the data file for future use. To save the contents of the Data Editor decide on a name for the data file. The current data refers to the Top Films of ALL Time. To save the contents of the Data Editor to the SPSS data file named Top Films, choose File >> Save As The Save Data As dialog box will open. SPSS 12 For Windows / Prepared By M. Zalzali /

28 Enter the name into the File name box and click the Save button. The data file will be saved as FrequencyR.sav in the chosen folder. SPSS can also export outputs as html file, text file, Excel file or Word/RTF file by choosing the selected options of Export ( Charts only, No charts, Output document ) SPSS 12 For Windows / Prepared By M. Zalzali /

29 8. REFERENCES [1] SPSS for Windows Manual By ROGER PECK, 6 th edition [2] SPSS handouts by Khalil Khalil, UGRU SPSS 12 For Windows / Prepared By M. Zalzali /