CHAPTER 6 CROSSTABS The Crosstab program will allow the user to tabulate any two variables using an SPPC raw data file. It will also produce a variety of statistics, raw frequencies, and percentages. The present version of the module is limited to the use of two-way tables. USING THE PROCEDURE The Crosstab module of the SPPC is very easy to use. The first thing to do is select the "Crosstab" option shown in the Master Menu of the SPPC program. When you do that, the Crosstab procedure will then be called into your computer memory. Crosstab allows you to use either categorical or continous data. If your data file contain continuous data you may easily categorize it into class intervals if you wish. Once you have entered the name of the your raw data file (preceded by drive and path if neccessary) and have confirmed the file selected, you will be prompted to select the two variables that you wish to tabulate. You may put either variable on the row or column dimension of the table. Even if your data file contains only two variables you will be prompted to select the variable you wish to use for each dimension. Crosstab cannot tabulate class intervals for only the second variable/dimension. However, it can tabulate class intervals for either the first variable/dimension only or both variables together. Should you decide to define class intervals, the program will first read your data file to determine the minimum and maximum values of the selected variables. Once that has been done you will be presented with a menu to define either the number of class intervals or the size of each class interval. The name of each variable is presented above the menu. If you wish to define class intervals for the first variable ONLY, make the appropriate selection at this menu and then press the '*' key when prompted to define class intervals for the second variable. The tabulation process will then begin. If you press the '*' at the first variable this tells the program that you wish to exit and will return you to the main Crosstab menu. After the data file has been read for the second time, or if you declined to define class intervals, you will be offered your choice of screen output: Summary Row Percentages Column Percentages Total Percentages Expected Values Final Statistics If you select SUMMARY output, Crosstab will display the cell frequencies for each of the two variables selected. If you select ROW PERCENTAGES, COLUMN PERCENTAGES or TOTAL PERCENTAGES, Crosstab will compute and display those respective percentages. If you select the EXPECTED VALUES option, Crosstab will display the expected values for each of the observed calculated cells. Please note that in all of the above displays, the marginal results reported are for the entire contingency program and do not represent page totals. Choosing FINAL STATISTICS will display the chi-square statistic, the associated degrees of freedom and chi-square probability. You will note that the Crosstab module will present your final tabulated data in pages having dimensions of 10 rows and 5 columns. If your table contains more than 10 rows and 5 columns, presentation will be from left to right and from top to bottom. That is, all computed columns will be presented for the first 10 or fewer rows. Then all columns will be presented for the next 10 or fewer rows and so forth. You may abort the display of your computed results by pressing the '*' key. However, it is important to note that the Crosstab program will save for later printing only those portions of the final output that you select. For example, let's assume that you've read a data file and that you wish to save only the Summary, Expected and Final results. Then you MUST select the Summary option, the Expected option and the Final option of the OUTPUT menu before exiting the program. DATA REQUIREMENTS The Crosstab procedure requires the use of a raw data file that has been created for use by the SPPC program. If you are not familiar with the structure of such files, please read Chapter 2 of the User's Manual. NUMBER OF CASES There is no practical limit to the number of cases that you may have in a raw data file. The theoretical limit is 30,000 cases. You may fill an entire diskette with a single data file and you may continue a data file onto two or more diskettes. You may use as many diskettes as you like. ESTIMATED CASES Under normal circumstances, the second line of your data file will contain the number of cases, the number of variables, and the letter R. If you show the number of cases to be zero (0), the procedure will count the number of cases in your file and then report that number to you. CAUTION: You may NOT estimate the number of variables. NUMBER OF VARIABLES The maximum number of variables that you may have in any raw data file is 200. However, you must select only two variables for actual processing. The program will automatically place you in the "variable selection" mode. SAMPLE OUTPUTS The following is sample output from the Crosstab procedure. If you wish, you may experiment with any of the raw data files that are provided with the SPPC program on the User's Manual diskette. ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ» º º º CROSS TABULATIONS º º º ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ» º º º Number of rows = 15 º º Number of columns = 10 º º Sample size = 502 º º Chi-square = 148.26741 º º º º df = 126 º º Probability [p] <= 0.08422 º º º º Pearson's C = 0.47750 º º Cramer's V = 0.18115 º º Tschuprow's T = 0.16221 º º º ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ The following are actual screen dumps generated by the Crosstab program. CROSS TABULATIONS Summary Variabletwo Variableone 1.00 2.00 3.00 4.00 5.00 Total 1.00 3 0 0 2 0 5 2.00 2 2 0 3 5 12 3.00 2 1 2 2 0 7 4.00 1 1 3 2 1 8 5.00 0 2 1 0 2 5 6.00 2 0 3 3 0 8 7.00 1 1 0 1 0 3 8.00 2 1 0 0 3 6 9.00 0 2 2 2 3 9 10.00 1 0 3 0 0 4 TOTAL 18 11 23 22 28 102 CROSS TABULATIONS Summary Variabletwo Variableone 1.00 2.00 3.00 4.00 5.00 Total 11.00 0 0 2 0 4 6 12.00 0 0 3 0 2 5 13.00 1 0 0 1 3 5 14.00 1 1 1 2 3 8 15.00 2 0 3 4 2 11 TOTAL 18 11 23 22 28 102 CROSS TABULATIONS Final Results Number of rows = 15 Number of columns = 5 Sample size = 102 Chi-square = 66.87417 df = 56 Probability [p] <= 0.15167 Pearson's C = 0.62929 Cramer's V = 0.40485 Tschuprow's T = 0.29599