Which of the following is the BEST study design for assessing the benefit of a...

The CBIC Certified Infection Control Exam Study Guide (6th edition) identifies the randomized controlled trial (RCT) as the gold standard study design for assessing the benefit of a new treatment. RCTs are specifically designed to determine causality by minimizing bias and confounding variables through random assignment of participants to intervention and control groups. This ensures that differences in outcomes can be attributed with the highest level of confidence to the treatment being studied rather than to external factors.

In an RCT, participants are randomly allocated to receive either the new treatment or a comparison intervention (such as standard therapy or placebo). Randomization balances known and unknown risk factors between groups, while controlled conditions allow precise measurement of treatment effects. This design is particularly important when evaluating new therapies, medications, or interventions where efficacy and safety must be clearly demonstrated.

The other study designs listed are less rigorous for assessing treatment benefit. An interrupted time series is useful for evaluating system-level interventions over time but is more susceptible to confounding influences. A correlational study can identify associations but cannot establish cause and effect. A parallel group study without randomization lacks adequate control for bias and confounding.

For CIC® exam preparation, it is essential to recognize that when the objective is to assess the benefit or effectiveness of a new treatment, a randomized controlled trial provides the strongest and most reliable evidence, making it the best answer.