Many data sets are challenging and time consuming to work with because the data are seldom in an optimal format.

So the question is what to do with your categorical variables. You have two choices, and each has advantages and disadvantages. The easiest is to put categorical variables in Fixed Factors. SPSS will dummy code those variables for you, which is quite convenient if your categorical variable has more than two categories. However, there are some defaults you need to be aware of that may or may not make this a good choice. SPSS always makes the reference group the one that comes last alphabetically. So if the values you input are strings, it will be the one that comes last. If those values are numbers, it will be the highest one.

Formatting Date Variables seems like it should be straightforward, but sadly, it’s not. If you are given data that includes dates, expect confusion. Dates can be represented in many different ways.

Moderated mediation, also known as Conditional Process Modeling, is great tool for understanding one type of complex relationship among variables.

How do you interpret the intercept in a regression model? The intercept is the expected mean value of Y when all X=0. This has different meanings, depending on the scale of X.

You might already be familiar with the binomial distribution. It describes the scenario where the result of an observation is binary—it can be one of two outcomes. You might label the outcomes as “success” and “failure” (or not!).

If you’ve used much analysis of variance (ANOVA), you’ve probably heard that ANOVA is a special case of linear regression. Unless you’ve seen why, though, that may not make a lot of sense. After all, ANOVA compares means between categories, while regression predicts outcomes with numeric variables.

A very common question is whether it is legitimate to use Likert scale data in parametric statistical procedures that require interval data, such as Linear Regression, ANOVA, and Factor Analysis. A typical Likert scale item has 5 to 11 points that indicate the degree of something. For example, it could measure agreement with a statement, […]

I’m a big fan of Analysis of Variance (ANOVA). I use it all the time. I learn a lot from it. But sometimes it doesn’t test the hypothesis I need. In this article, we’ll explore a test that is used when you care about a specific comparison among means: Dunnett’s test.

Data analysts can get away without ever understanding matrix algebra, certainly. But there are times when having even a basic understanding of how matrix algebra works and what it has to do with data can really make your analyses make a little more sense.