Cheat Sheet
SPSS Statistics For Dummies Cheat Sheet
IBM SPSS Statistics is an application that performs statistical analysis on data. In order to perform statistical analyses correctly, you need to know the level of measurement of the variables because it defines which summary statistics and graphs should be used. It also helps to know the most commonly used procedures within the Analyze menu and possible conclusions that you can reach after conducting a statistical test.
SPSS Statistics Variables Level of Measurement
In SPSS Statistics, the level of measurement of the variables defines which summary statistics and graphs should be used. The following table provides definitions, examples, appropriate summary statistics, and graphs for the level of measurement of the variables.
Nominal | Ordinal | Scale | |
---|---|---|---|
Definition | Unordered categories | Ordered categories | Both interval and ratio |
Examples | Gender, geographic location, job category | Satisfaction ratings, income groups, ranking of preferences |
Number of purchases, cholesterol level, age |
Measures of Central Tendency | Mode | Median | Median or mean |
Measures of Dispersion | None | Min/max/range | Min/max/range, Standard deviation/ variance |
Graph | Pie or bar | Bar | Histogram |
SPSS Statistics Charts to Show Relationships between a Pair of Variables
When choosing a graph to show the relationship between variables, you need to know the level of measurement of the variables. The following table shows some of the graphs that can be used to display relationships between different types of variables.
Categorical Dependent | Scale Dependent | |
---|---|---|
Categorical Independent | Clustered bar or paneled pie | Error bar or boxplot |
Scale Independent | Error bar or boxplot | Scatter plot |
SPSS Statistics Commonly Used Analyze Menus
The following table provides a list of some of the most commonly used procedures within the Analyze menu of IBM SPSS Statistics, which is an application that performs statistical analysis on data.
Submenu | Useful For . . . | |
---|---|---|
Code Book | Reports | A quick look at all your variables at once. Level of measurement automatically controls which summary statistics are displayed. |
Frequencies | Descriptives | Most useful for categorical variables. You can run all of them at once. Tells you how many of each category value you have. |
Descriptives | Descriptives | Easy way to get basic scale variable info like mean and median. |
Explore | Descriptives | Based on a famous book, Exploratory Data Analysis. An effective way to look at all kinds of variables, as well as pairs of variables. |
Crosstabs | Descriptives | A test to check to see if categorical variables are independent of each other or related to each other. |
Means | Compare Means | Calculates subgroup means and related statistics for dependent variables within categories of one or more independent variables. |
One-Sample T-Test | Compare Means | Tests whether the mean of a single variable differs from a specified value (for example a group using a new learning method compared to the school average). |
Independent Samples T-Test | Compare Means | Tests whether the means for two groups differ on a continuous dependent variable (for example, females versus males on income). |
Paired Samples T-Test | Compare Means | Tests whether there is a significant difference in the mean under two conditions (for example, before versus after, or standing versus sitting). |
One way ANOVA | Compare Means | Tests whether the means for two or more groups differ on a continuous dependent variable (for example, drug1 versus drug2 versus drug3 on depression). |
Bivariate Correlation | Correlate | Correlations determine the similarity or difference in the way two continuous variables change in value from one case (row) to another through the data. |
Linear Regression | Regression | A statistical technique that is used to predict a continuous dependent variable from one or more continuous independent variables. |
Interpreting Statistical Significance in SPSS Statistics
You need to know how to interpret the statistical significance when working with SPSS Statistics. When conducting a statistical test, too often people immediately jump to the conclusion that a finding “is statistically significant” or “is not statistically significant.” While that is literally true, it does not imply that there are only two conclusions to draw about a finding.
What if in the real world there is no relationship between the variables, and the test found that there was a significant relationship? In this case, you would be making an error; this type of error is called a “false positive” because you falsely conclude a positive result (think it does occur).
On the other hand, what if in the real world there is a relationship between the variables, and the test found that there was no significant relationship? In this case, you would be making an error; this type of error is called a “false negative” because you falsely conclude a negative result (think it does not occur).
In the Real World | Statistical Test Results | |
---|---|---|
Not Significant (p > 0.5) | Significant (p < 0.5) | |
The two groups are not different | The null hypothesis appears true, so you conclude the groups are not significantly different. |
False positive. |
The two groups are different | False negative. | The null hypothesis appears false, so you conclude that the groups are significantly different. |