Randomization procedures in single‐case intervention research contexts: (Some of) “the rest of the story”

Following up on articles recently published in this journal, the present contribution tells (some of) “the rest of the story” about the value of randomization in single‐case intervention research investigations. Invoking principles of internal, statistical‐conclusion, and external validity, we begin by emphasizing the critical distinction between design randomization and analysis randomization, along with the necessary correspondence between the two. Four different types of single‐case design‐and‐analysis randomization are then discussed. The persistent negative influence of serially dependent single‐case outcome observations is highlighted, accompanied by examples of inappropriate applications of parametric and nonparametric tests that have appeared in the literature. We conclude by presenting valid applications of single‐case randomization procedures in various single‐case intervention contexts, with specific reference to a freely available Excel‐based software package that can be accessed to incorporate the present randomization schemes into a wide variety of single‐case intervention designs and analyses.     

临床医学类学术论文应正确使用“随机化”

"随机化"是科学研究的基本原则之一,是研究结果外推的重要保证。虚假"随机化"把偶然现象上升为规律,极大地玷污了科学研究的客观真实性,危害无穷。本文以具体的案例剖析了临床研究论文"随机化"的误用和乱用,并提出了应对的措施。     

Randomization tests in single-subject designs: Illustrative examples

Randomization tests have recently been adapted for use in the analysis of single-subject data. The advantages of these tests lie in their ease of implementation and interpretation as well as their freedom from underlying distributions. Even though numerous articles and books have explicated randomization test procedures, due to the lack of appropriate examples, very little use of these procedures has been made by applied behavior analysts. Data sets reported in a prominent applied behavior journal are used to demonstrate the application of randomization tests to the following three single-subject design models: (a) two-phase random intervention point, (b) multiple phase, and (c) multiple phase with a predicted order of effect size.     

Some Thoughts Regarding the Sensitivity of t to Error in Estimated Within-Group Variance

A. J. Riopelle (2003) has eloquently demonstrated that the null hypothesis assessed by the t test involves not only mean differences but also error in the estimation of the within-group standard deviation, s. He is correct in his conclusion that the precision of the interpretation of a significant t and the null hypothesis tested is complex, particularly when sample sizes are small. In this article, the author expands on Riopelle's thoughts by comparing t with some equivalent or closely related tests that make the reliance of t on the accurate estimation of error perhaps more salient and by providing a simulation that may address more directly the magnitude of the interpretational problem.     

Patient Perspectives on the Learning Health System: The Importance of Trust and Shared Decision Making

We conducted focus groups to assess patient attitudes toward research on medical practices in the context of usual care. We found that patients focus on the implications of this research for their relationship with and trust in their physicians. Patients view research on medical practices as separate from usual care, demanding dissemination of information and in most cases, individual consent. Patients expect information about this research to come through their physician, whom they rely on to identify and filter associated risks. In general, patients support this research, but worry that participation in research involving randomization may undermine individualized care that acknowledges their unique medical histories. These findings suggest the need for public education on variation in practice among physicians and the need for a collaborative approach to the governance of research on medical practices that addresses core values of trust, transparency, and partnership.     

An empirical investigation of the statistical properties of generalized single-case randomization tests

Adapting Edgington's [J. Psychol. 90 (1975) 57] randomly determined intervention start-point model, Levin and Wampold [Sch. Psychol. Quart. 14 (1999) 59] proposed a set of nonparametric randomization tests for analyzing the data from single-case designs. In the present study, the performance of Levin and Wampold's four basic tests (independent start-point general and comparative effectiveness, simultaneous start-point general and comparative effectiveness) was examined with respect to their Type I error rates and statistical power. Of Levin and Wampold's four tests, all except the independent start-point comparative effectiveness test maintained their empirical Type I error rates and had acceptable power at larger sample-size and effect-size combinations. The one-tailed comparative intervention effectiveness test for the independent start-point model was found to be too liberal, in that it did not maintain its Type I error rate. Although a two-tailed application of that test was found to be conservative at longer series lengths, it had acceptable power at larger sample-size and effect-size combinations. The results support the utility of a versatile new class of single-case designs that permit both within- and between-unit statistical assessments of intervention effectiveness.     

临床均势原则辨析——对临床科研方法的伦理思考

随机对照试验作为一种评价新疗法的可靠设计方法,开始逐渐被世界范围内的临床医生所广泛接受和采用,成为目前最重要的试验方法之一。RCT的运用应该遵循一定的伦理准则,即临床均势原则。围绕临床均势原则这一主题,对随机对照试验的方法论进行较为深入的伦理学思考。并对临床均势的内涵、伦理意义,以及这一伦理要求在实践中所引发的各种伦理争论加以探讨。     

Randomization tests as alternative analysis methods for behavior‐analytic data

Randomization statistics offer alternatives to many of the statistical methods commonly used in behavior analysis and the psychological sciences, more generally. These methods are more flexible than conventional parametric and nonparametric statistical techniques in that they make no assumptions about the underlying distribution of outcome variables, are relatively robust when applied to small‐n data sets, and are generally applicable to between‐groups, within‐subjects, mixed, and single‐case research designs. In the present article, we first will provide a historical overview of randomization methods. Next, we will discuss the properties of randomization statistics that may make them particularly well suited for analysis of behavior‐analytic data. We will introduce readers to the major assumptions that undergird randomization methods, as well as some practical and computational considerations for their application. Finally, we will demonstrate how randomization statistics may be calculated for mixed and single‐case research designs. Throughout, we will direct readers toward resources that they may find useful in developing randomization tests for their own data.     

Both Sides of the Coin: Randomization from the Perspectives of Physician-Investigators and Patient-Subjects

Randomization is the “gold standard” design for clinical research trials and is accepted as the best way to reduce bias. Although some controversy remains over this matter, we believe equipoise is the fundamental ethical requirement for conducting a randomized clinical trial. Despite much attention to the ethics of randomization, the moral psychology of this study design has not been explored. This article analyzes the ethical tensions that arise from conducting these studies and examines the moral psychology of this design from the perspectives of physician-investigators and patient-subjects. We conclude with a discussion of the practical implications of this analysis.     

A replication of preference displacement research in children with autism spectrum disorder

The purpose of this paper was to replicate previous research on preference displacement with edible and leisure stimuli. In the present study, the experimenters evaluated preference displacement in 25 children with autism spectrum disorder using combined multiple stimulus without replacement preference assessments that consisted of highly preferred edible and leisure stimuli. In addition, the experimenters used a block randomization procedure to evaluate if assessment order influenced displacement outcomes. The experimenters observed patterns of complete displacement by edible stimuli for four participants and complete displacement by leisure stimuli for two participants; assessment order did not influence outcomes. The results and implications are discussed.