D.5: Identify the relative strengths of single-case experimental designs and group designs.
Free practice questions for this part of the BCBA, with an explanation for every option.
A clinic director asks why her team uses single-case designs rather than comparing the average outcomes of a treated group and an untreated group. Which is a real advantage of single-case designs?
- A. They allow statistical generalization to a population through random samplingIncorrect. Random sampling and statistical inference to a population are strengths of group designs.
- B. They answer actuarial questions about how a program affects an entire school districtIncorrect. Questions about aggregate, population-level effects are better suited to group designs.
- C. They show each individual's response to treatment, which group averages can hideCorrect. Because single-case designs analyze each person's data, they show whether a given individual improved, worsened, or did not change, which group means can mask.
- D. They need fewer measurements per participant than group designsIncorrect. Single-case designs rely on repeated measurement, so they usually need more measurements per participant, not fewer.
A state agency wants to know whether, on average, students in 200 schools that adopt a new classroom-management program have fewer office referrals than students in comparable schools that do not. Which approach best fits this question?
- A. A group comparison design, because the question concerns average effects across a large populationCorrect. Questions about average, aggregate effects across many units (actuarial questions) are what group designs are built to answer.
- B. A multielement design with each school, because it rapidly compares conditionsIncorrect. Multielement designs evaluate effects for individuals with rapidly alternating conditions. They are not suited to comparing averages across hundreds of schools.
- C. An A-B-A-B design with one student, because it gives the strongest demonstration of controlIncorrect. One student's data cannot answer a question about average effects across 200 schools, however strong the experimental control.
- D. A changing-criterion design, because referrals should decrease in stepsIncorrect. A changing-criterion design evaluates stepwise performance criteria for an individual and does not address average population effects.
In a home-based program, a BCBA reviews a 4-year-old's data after each session. She changes the prompting procedure as soon as progress stalls. Compared with a typical group design that collects pretest and posttest scores, which feature of single-case designs makes this possible?
- A. Statistical tests that compare the means of large samplesStatistical comparison of group means is typical of group designs and does not support session-by-session decisions.
- B. Random assignment of participants to treatment and control groupsRandom assignment is a feature of group designs. It does not help with day-to-day treatment decisions for one child.
- C. Repeated measurement of the individual's behavior across timeCorrect. Single-case designs measure one person's behavior repeatedly, so the practitioner can see each change in level, trend, or variability and adjust treatment right away.
- D. A single measurement taken after the intervention endsA single posttest gives no information during treatment, so it cannot guide ongoing changes.