How to Create an Interaction Plot in SPSS

What Is an Interaction Plot? An interaction plot (also called a profile plot in SPSS) is a line graph that shows how the effect of one factor on your outcome changes across the levels of another factor — the clearest way to see whether two variables interact. If you have not run the analysis yet,

Pearson vs Spearman: Which Correlation Do You Need?

Two Correlations, One Decision You have two variables and one question: are they related? In SPSS, that question usually leads to one of two tests — Pearson’s correlation or Spearman’s rank correlation. They look similar, they sit next to each other in the same dialog box, and they both produce a number between −1 and

Q-Q Plots and Shapiro-Wilk: Checking Normality in SPSS

Why Checking Normality Matters Before You Run a Test Almost every parametric test in SPSS — the independent-samples t-test, one-way ANOVA, Pearson correlation, linear regression — comes with a small-print condition: your data should be approximately normally distributed. Skip that check and you risk reporting a p-value from a test whose assumptions your data never

Fisher’s Exact Test in SPSS: When Chi-Square Fails

The chi-square test is the default choice for testing whether two categorical variables are related. But it relies on an approximation that breaks down when your sample is small. When one or more cells in your table have very low expected counts, the p-value chi-square gives you can be misleading. That is exactly when Fisher’s