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Kukucka Stats 1

Introduction to SPSS

SPSS is your new best friend. No, seriously. It will make your statistics life much, much easier, because it can save you from having to do lots of tedious math. However, it can be confusing at first, so it will be helpful for us to spend today getting to know the basics of SPSS.

What is a Variable?

A variable is any characteristic that can vary between people. For example, people vary in terms of gender, age, IQ score, alcohol use, and about a billion other things that make individuals different from each other.

As researchers, sometimes we have control over these variables (e.g., we can give people alcohol to change their level of alcohol use), but sometimes we don’t (e.g., we can’t control a person’s age or gender).

Practice: Johnny is a six year-old Asian boy with an IQ of 110. How many different variables have we used to describe Johnny? List each of these variables in the space below.

Types of Variables

Variables are typically measured in one of two ways. Categorical variables consist of categories (also called “levels”), with each person falling into one (and only one) category. For example, gender is a categorical variable with two levels (male and female); every individual falls into one of these categories.

In contrast, continuous variables are numerical measurements, where a person’s score can be any number within a given range. For example, age is a continuous variable: It is a number (usually measured in years), and any given person’s score can be any number between (usually) 0 and 100 years.

Practice: Name three examples of categorical variables and three examples of continuous variables below. Categorical Variables: Continuous Variables:

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Kukucka Stats 2

Variable View in SPSS

Under the “Variable View” tab in the bottom-left corner, SPSS shows a list of all of the variables for which you have data. When you are entering data, the first thing you will do is list all of the variables that you have. For example, if we wanted to enter the data for Johnny, we would first need to create our variables...

1) Under Name, we give each variable a name. Variable names should be short and descriptive (ideally one word, or two words/abbreviations, with no spaces). So, with something like “age,” we can simply call it “age.”

2) Sometimes it is hard to capture what a variable means in a single word or two. When this happens, we can also add a Label that gives a more detailed description of what that variable is measuring.

For example, we might not know what “IQ” means just from looking at its Variable Name. So, we have added a Variable Label to clarify that the variable “IQ” indicates each person’s “Intelligence Score.”

3) Under Measure, we tell SPSS whether each variable is continuous (i.e., “Scale”) or categorical (i.e., either “Nominal” or “Ordinal”). So, for example, “age” is a continuous variable, whereas “race” is categorical.

4) Then, for each categorical variable, we have to assign a number to each category or “level” of that variable.

To do this, click under the Values column in the row that contains your categorical variable. A window will pop up that looks like the one on the left.

Under “Label,” type the name of a category. Then, under “Value,” assign a number (any number) to that category. Finally, click “Add.” Repeat this process for every possible category, and then click OK. For example, I have (arbitrarily) designated “White” as “1,” “Black” as “2,” “Hispanic” as “3,” and so on. This will be important when we enter the data.

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Kukucka Stats 3

Practice: Imagine that we want to create a variable that tells us whether or not a person owns a car. Use the space below to indicate what you would put in each of these columns under Variable View in SPSS. Variable Name: ___________________________ Variable Label: _______________________________________________________________________ Measure (Nominal or Scale?): ___________________________ Values (if necessary): A value of _________ means __________________________________. A value of _________ means __________________________________.

Data View in SPSS

Once we have created all of our variables under “Variable View,” we can now enter our data. Switch to “Data View” using the button at the bottom left. You will notice that each of the Variable Names that we just created now appears as a column in our datafile. So, each column will contain all of the data for a given variable. Each row will contain all of the data (i.e., variables) for a given person. For Johnny, we would enter his age (6), race (4), gender (1), and IQ (110) in row #1. Notice that for categorical variables, we have to enter the numerical value that we assigned to whichever category that person is in. So, we put “4” for Johnny’s race because we designated “Asian” as “4” under Variable View.

To make life easy, SPSS automatically replaces our “4” with the label “Asian” so that we don’t have to remember what “4” means. (if this isn’t happening, go to “View” and check the “Value Labels” box.) All of Johnny’s data goes in row #1. Our second person then would go in row #2, our third in row #3, and so on. Practice: How would you describe the person in Row #2? What numbers would you enter (from left to right) in row #3 if the next person was a four year-old White female with an IQ of 95?