DDBA 8438: Frequency Distributions Video Podcast Transcript *JENNIFER ANN MORROW: Welcome to "Frequency Distributions." My name is Dr. Jennifer Ann Morrow. Today in this demonstration, I will show you how to conduct frequencies in SPSS. I will also show you how to read a frequency distribution table and understand the types of percentages displayed in a frequency distribution table. I will also show you how to create charts and graphs in SPSS, specifically how to create bar charts, histograms, pie charts, and line graphs. Okay, let's get started. Frequency Distribution JENNIFER ANN MORROW: Now that I have my SPSS data set open, the first thing that I'm going to show you how to do is to create frequency distribution tables in SPSS. First, click on Analyze, click on Descriptive Statistics, and click on Frequencies. As you can see, the Frequency dialog box is now open in SPSS. On your left is the list of variables that you have in your data set, and on the right is the blank analysis box where you will put the variables that you want to use for your analysis. Now let's display some frequency tables for a couple of our variables. I'm going to select Gender, and then once I click on Gender, I'm going to click on the right arrow box. And then I'm also going to select School Grade and then click on the right arrow. Now, both of my variables appear in my analysis box on the right. Remember, you can always click on Paste to put syntax in a syntax window and run the analysis that way, or you can just click Okay and have SPSS immediately conduct your analysis. So let's click on Okay. Now an output window appears with the results of your analysis. Let's just scroll up to the top of your output file. As you can see in your output window, SPSS will first give you a table that gives the total N for both of the variables. In this data set, we have 1,637 participants that have a valid value for gender and 9 participants that have missing data for this particular variable. For School Grade, we have 1,641 participants that have a valid value for School Grade and 5 participants that are missing data for School Grade. Now let's scroll down to the first frequency table. As you can see with our variable Gender, we have our variable coded as follows: zero is for females, and 1 is for males. In this data set, we have 928 females and 709 males for a total of 1,637 participants that have a valid value for the

variable Gender. One thing I want to point out to you is the difference between this Percent column and the Valid Percent column. Percentages JENNIFER ANN MORROW: For the percent column, this is the value that is the total number of participants in one category divided by the total number of participants in your data set, and then multiply that value by 100 in order to get the percent. In the case for females, we take 928, divide that by 1,646, and multiply that by 100 in order to get a percent of 56.4. So in this data set, 56.4% of our participants are females. The valid percent is different in that it takes out all of the missing data before calculating the percentage. So in this case, to get the valid percent for females, you take the value of 928, divide that by 1,637, and multiply that by 100 in order to get the valid percent of 56.7%. The only time that the values and the percent in the Valid Percent column will be equal is if you have no missing data for that variable. Now let's move on to our other frequency distribution table for School Grade. Let's scroll down through our output. For our variable School Grade, we can see we have students from the 7th grade to the 12th grade as well as one participant that was ungraded. In this data set, we have 1,641 participants that have a response for School Grade and only five participants that do not have a response for School Grade. Now I want to show you in this table the Cumulative Percent column. The Cumulative Percent column adds the valid percent values for each successive category. For example, if you add the valid percent for seventh graders, 0.2, and the percent for eighth graders, 9.1, you will get a cumulative percent of 9.4. As you can see, there's some rounding issues with this. But if you click on the box for the valid percent, you will see the exact number for the valid percent and not just the value that was rounded up or down. Let me show you what I mean. You double-click on your chart, and double-click on the valid percent of the seventh graders. As you can see, the exact value is 0.2437, et cetera. Now double-click on the value for eighth graders. And that valid percent is 9.1407, et cetera. If you add those two values together, you will get the cumulative percent, here listed as 9.4. If you double-click on the box, the exact value: 9.3845, et cetera. Again, SPSS rounds up to make things easier to read in your table. Missing Data

JENNIFER ANN MORROW: The last thing I want to mention before moving on is to make sure that you pay attention to the missing data in your variables. It is very important to know how much missing data is in each of your variables. The more missing data that you have, the fewer participants you will have to conduct your analyses. In the case of School Grade, we only have 5 participants that don't have a value for School Grade, or much less than 1% of our total participants in our data set. Always be aware of the number of missing data points you have for each variable. Recap JENNIFER ANN MORROW: Let's recap. First, we learned how to display frequency distributions in SPSS. We talked about the differences between percent and valid percent. We also discussed what a cumulative percent is. Lastly, I mentioned the importance of knowing how much missing data you have in your variables. Now let's move on to creating charts and graphs. Displaying Frequencies in Charts and Graphs JENNIFER ANN MORROW: Now that I'm back in my SPSS data set, let me show you how to create charts in SPSS. We can create charts in SPSS in two different ways. First, we can ask for them in our Frequency Distribution dialog window, or we can go under the Graph function in SPSS. First, I'm going to show you how to get charts using your Frequency dialog box. Click on Analyze, Descriptive Statistics, and Frequencies. And as you can see, our Frequency dialog box will open up, showing our last analysis. Remember, we just did a frequency distribution for Gender and School Grade. So now let me show you how to create a chart for the variable Gender. So, first, I'm going to click on School Grade and click on the left arrow button to move that back over to the list on the left, because I only want to look at the variable Gender. Now I'm going to show you how to create various charts for the variable Gender. Click on Charts. And as you can see, there are a few options here under Charts. For the variable Gender, since it is a categorical variable or a discreet variable, only bar charts or pie charts are appropriate. It is not appropriate to do a histogram for a variable that is not continuous.

Bar Chart JENNIFER ANN MORROW: So, first, let me show you how to create a bar chart for Gender. Click on Bar Chart. You'll notice here, at the bottom, where it says "Chart Values," that you have the option of displaying either the frequencies or the percentages for your bar chart. I would like to display the frequencies, so I'll keep that checked and then click on Continue. Then I would click on Okay so SPSS will create a chart for Gender. As you can see, SPSS has created a bar chart for the variable Gender. And you can modify this chart however you like, again, by double-clicking the chart in order to get the Chart Editor. Pie Chart JENNIFER ANN MORROW: So if I double-click my chart, I now get the Chart Editor. And you can do many different things here. You can create new titles. You can change the color of your bars in your chart. Let me close out the Chart Editor and move on to show you how to do another chart. Next, I want to show you how to create a pie chart in SPSS. Click on Analyze, Descriptive Statistics, Frequencies. We already have the variable Gender here in our analysis box. Click on Charts, and now click on Pie Charts. Again, I'm going to stick with frequencies for this analysis. I'll click on Continue, and then now, let's click on Okay. SPSS, as you can see, has created a pie chart for my variable Gender of Participant. As you can see, SPSS will automatically create a slice of the pie for those participants that have missing data. You can easily modify the chart so it does not display participants that have missing data. Double-click on your chart. Click on Edit; click on Properties. Click on Categories. Click on where it says "Missing." Click on the red X so it takes out the pie slice for the variable the category Missing. And then click on Apply. And we'll close this box, and as you can see now, you have a pie chart that just displays participants that have a value for female and a value for male. Lastly, under the Frequencies dialog box, let me show you how to create a histogram. Click on Analyze, Descriptive Statistics, Frequencies. Histogram

JENNIFER ANN MORROW: Let's click Reset to get rid of the last analysis that we conducted so we can start fresh. Let's go over to our box on the left and scroll down and click on Hours Per Week at Job, the second-to-the-last variable here. Click on the right arrow key. And now we're going to click on Charts and click on Histograms. And I always like to display the normal curve, so click on the box that says "With Normal Curve." Click on Continue, and then click on Okay. And as you can see, SPSS has created a histogram for this variable, Number of Hours Per Week at Job. A histogram is appropriate for this type of variable because it is a continuous variable. Bar Graph JENNIFER ANN MORROW: Next, I would like to show you how to create charts using the graphs function in SPSS. Click on Graphs, and you'll see that there's a variety of graphs available to you in SPSS. First, I want to show you how to create a bar graph under this function. So scroll down and click on Bar. Then you see you have three different choices: Simple, Clustered, and Stacked. Click on Simple, and then click on Define. Now let's click on a variable to create a bar chart. I'm going to choose Gender, so click on Gender, and then move that over here to where it says "Category Axis." You can also enter a title for your bar chart. If you go down here on the right and click on Titles, you can enter a title for your chart. I'll enter "Gender of Participant." Once you've entered your title, click on Continue. Now click on Okay. As you can see, you'll get a bar chart very similar to the one we've already created under the Frequency dialog box. Histogram JENNIFER ANN MORROW: We could also ask for histograms under the Graphs menu in SPSS. Click on Analyze-- I mean, click on Graphs. Excuse me. Click on Histogram. And now we get the Histogram dialog box in SPSS. Click on a variable that is continuous. How about I choose Hours Per Week Doing Chores? And then click the right arrow key for the variable box, moving that variable, Hours Per Week Doing Chores, into the variable window. Again, I always like to display the normal curve. Click on the Titles box at the right so you can enter a title, "Hours Per Week Doing Chores." Once you've entered your title, click Continue, and then click Okay. As you can

see, SPSS will display a histogram for this continuous variable, Hours Per Week Doing Chores. You also have the freedom with this type of chart to double-click to get the Chart Editor to modify your chart in many ways. Now let me show you how to ask for a pie chart in SPSS. Click on Graphs; click on Pie. Then click on Define. Now choose a variable that you want to create a pie chart for. Let me choose the variable Whom Do They Live With? Click on that variable. Click on the right arrow key for Define Slices By so the variable Whom Do They Live With appears there. Click here on the right, Titles, to enter a title for your pie chart, "Whom Do They Live With." Once you've entered your title, click on Continue. And then click on Okay. And as you can see, for this variable, Whom Do They Live With, there are a variety of categories, from Mother and Stepfather, Father and Stepmother, et cetera. And, again, you have the freedom in SPSS to double-click on the chart to modify any of the properties using your Chart Editor. Line Graph JENNIFER ANN MORROW: Lastly, I want to show you how to create a line graph in SPSS. Click on Graphs, click on Line, and you see you have three choices: Simple, Multiple, and Drop Line. I'll choose Simple and then click on Define. Now I have to choose a variable. Let's click on the variable Hours Per Week at Job. Over here on the right, click Other Statistic. Then click the right arrow box next to the variable window, and this will now display the mean for hours per week at someone's job. This will represent, then, the mean hours per week in your line graph. I would like SPSS to display a line graph displaying the mean hours per week at a job for both males and females. So I click on my variable over here on the left, Gender, and click on the right arrow key for Category Axis. This will then tell SPSS to give me a line graph that displays the mean hours per week for females and the mean hours per week for males. Again, I can always go to the box on the right, click on Titles, to enter a title for this line graph. "Gender and Hours Per Week at Job." Once you've entered your title, click on Continue, and then click on Okay. SPSS will display a line graph that connects the mean for females for hours per week at job and the mean for males. As you can see here in your graph, the mean for females at hours per week at job is a little bit above 2.5 hours per week, and for males, the mean is a little bit above 3.0 hours per week. SPSS automatically connects those two

means and draws a line representing the mean hours per week for both females and males. Recap JENNIFER ANN MORROW: Now let's recap. We went over displaying percentages versus frequencies in your charts and graphs. We next learned how to display bar charts, histograms, pie charts, and line graphs. We are now at the end of this demonstration. Remember to practice what we learned today. On your own, use SPSS to create frequency tables and charts and graphs. Practice modifying your charts and graphs using your Chart Editor. Thanks, and have a great day.