What statistical test should be used for continuous data from three or more related samples?

The appropriate statistical test for continuous data collected from three or more related samples is a Two-Way ANOVA. This test extends the One-Way ANOVA by allowing researchers to assess the influence of two independent variables on a single dependent variable, as well as the interaction effects between these two variables.

When dealing with related samples specifically, a repeated measures design is often used, which can be conveniently analyzed with a Two-Way ANOVA. This kind of analysis provides insight into how different treatments or conditions affect the response variable while accounting for possible interactions between the two factors analyzed.

In this context, the test effectively compares means among the groups and helps determine if there are statistically significant differences attributable to both factors being studied, thus making it suitable for this scenario.