Which of the following is NOT a feature of a mixed design?

• A. It involves both between-subjects and within-subjects manipulations.
• B. It uses only between-subjects comparisons.
• C. It is also known as split-plot design.
• D. It cannot involve any between-subjects manipulation.

Answer: (D)

Mixed designs combine a between-subjects factor with a within-subjects factor, so you can compare different groups and also track changes within the same participants across conditions. Saying that a mixed design cannot involve any between-subjects manipulation goes against this setup, because the between-subjects element is essential to a mixed design. If there were no between-subjects manipulation, you’d simply have a within-subjects (repeated measures) design, not a mixed one. The other statements describe real features of mixed designs: they include both kinds of manipulations, and they’re often called a split-plot design. For example, you might compare two or more dose groups (between-subjects) and measure responses across multiple time points (within-subjects). The analysis would examine main effects for dose and time and their interaction.