Potential setting-level events include staffing changes in classroom, redecoration or renovation of the physical environment, and changes in the composition of the peer group in a classroom, group home, or worksite. One area that has, in the past, been particularly controversial is the experimental rigor of concurrent versus nonconcurrent multiple baseline designs; that is, the degree to which each can rule out threats to internal validity. Slider with three articles shown per slide. (Our specification of phase change offset in terms of real time, days in baseline, and sessions in baseline is unusual. If either of these assumptions are not valid for a coincidental event, then the presence and function of that event would not be revealed by the across-tier analysis. They then describe the multiple baseline technique (p. 94) and two types of comparisons that contribute to its experimental control. With control for coincidental events in multiple baseline designs resting squarely on replicated within-tier comparisons, there is no basis for claiming that, in general, concurrent designs are methodologically stronger than nonconcurrent designs. Perhaps a more general and powerful triad of processes that support demonstration of experimental control would be prediction, contradiction, and replication. These reports do not provide the information necessary to rigorously evaluate maturation or coincidental events. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. By nature, undetected events are unknown. Characteristics of single-case designs used to assess intervention effects in 2008. This argument rests on the assumptions that any extraneous variable that affects one tier will (1) contact all tiers and (2) have a similar effect on all tiers. This would align the definition with the critical features required to demonstrate experimental control and thereby allow strong causal statements based on multiple baseline designs. In addition, arranging tiers that are isolated in other dimensions (e.g., location, behaviors, participants) confers overall strength, not weakness, for addressing coincidental events. Part of Springer Nature. Smith, J. D. (2012). The across-tier comparison of concurrent multiple baseline designs is less certain and definitive than it may appear. Therefore, researchers must exercise extreme caution in interpreting and generalizing the results from pre-experimental studies. When changes in data occur immediately after the phase change, are large in magnitude, and are consistent across tiers, threats to internal validity tend to be less plausible explanations of the data patterns, and fewer tiers would be required to rule them out. Kennedy, C. H. (2005). In a review of the SCD literature, Shadish and Sullivan (2011) found multiple baseline designs making up 79% of the SCD literature (54% multiple baseline alone, 25% mixed/combined designs). (1968) who emphasized the replicated within-tier comparison. Kazdin and Kopel (1975) parallel much of Hersen and Barlows (1976) commentaryFootnote 3 but they also point out an apparent contradiction in the assumptions about behavior on which the multiple baseline design is built. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. In particular, within-tier comparisons may be strengthened by isolating tiers from one another in ways that reduce the chance that any single coincidental event could coincide with a phase change in more than one tier (e.g., temporal separation). Further, for the across-tier comparison to detect the influence of a coincidental event, that event must not only contact multiple tiers, it must cause similar changes in the dependent measure across multiple tiers. (1981). A given period of maturation may affect various participants, various behaviors, or behaviors in various settings in different ways. To understand the ability of concurrent designs to meet these assumptions we must distinguish different types of coincidental events based on the scope of their effects. As Kazdin and Kopel (1975) pointed out, multiple baseline designs require that the effects of the independent variable must have tier-specific effects, yet the across-tier analysis requires that extraneous variables must not have tier-specific effects. Nonconcurrent multiple baseline designs for educational program evaluation. A potential treatment effect in any single tier could plausibly be explained as a result of a coincidental event. In order to demonstrate experimental control, the researcher makes two paradoxical assumptions. WebGive two advantages and two disadvantages of quasi-experimental designs. Basic Books. Wacker, D., Berg, W., Harding, J., & Cooper-Brown, L. (2004). Research methodologists have identified numerous potential alternative explanations that are threats to internal validity (e.g., Campbell & Stanley, 1963; Cooper et al., 2020; Kazdin, 2021; Shadish et al., 2002). Applied behavior analysis (3rd ed.). Kazdin, A. E. (2021). Third, we explore how concurrent and nonconcurrent multiple baselines address each of the main threats to internal validity. Any alternative explanation of this pattern of results would have to posit an alternative set of causes that could plausibly result in changes in the dependent variable in this specific pattern across the multiple tiers. Rather, the passage of time allows for more opportunities for participants to interact with their environmentleading to maturational changes. Peer reviewers and editors who serve as gatekeepers for the scientific literature must also have a deep understanding of these issues so that they can distinguish between stronger and weaker research, ensure that information critical to evaluating internal validity is included in research reports, and assess the appropriateness of discussion and interpretation of results. Second, in a remarkably understated reference to the across-tier comparison, Baer et al. How many tiers do we need? Some current dimensions of applied behavior analysis. https://doi.org/10.1023/B:JOBE.0000044735.51022.5d, Hayes, S. C. (1981). The use of continuous assessment and multiple experimental phases in single-subject research designs allow for detailed examinations of Type I errors and power in multiple baseline designs. The current SCD methodological literature and most SCD textbooks claim that because the tiers of nonconcurrent multiple baseline are not synchronized in real time they have a diminished capacity to control for extraneous variables, in particular coincidental events (e.g., Carr, 2005; Gast et al., 2018; Harvey et al., 2004; Johnston et al., 2020). Ten sessions of baseline would be expected to have similar effects whether they occur in January or June. Without these dimensions of lag explicitly stated in the definition, we cannot claim that multiple baseline designs will necessarily include the features required to establish experimental control. Such events might be said to contact all tiers, but affect only one of them. This controversy began soon after the first formal description of nonconcurrent multiple baseline designs by Hayes (1981) and Watson and Workman (1981). Journal of Consulting & Clinical Psychology, 49(2), 193211. (p. 365), Of course, the major problem with this [nonconcurrent multiple baseline] strategy is that the control for history (i.e., the ability to assess subjects concurrently) is greatly diminished. B. If a potential treatment effect is seen in one tier and on the same day there is no change in other tiers, this is taken as strong evidence that the potential treatment effect was not a result of a coincidental event, because a coincidental event would have had an effect on all tiers. PubMedGoogle Scholar. First, studies differ with respect to the experimental challenges imposed by the phenomena under study. The assumption that all tiers respond similarly to maturation may be somewhat more problematic. When he turned to multiple baseline designs, Hayes argued that AB designs are natural to clinic work and that forming a multiple baseline can consist of collecting several AB replications, which would inevitably have differing lengths of baseline (i.e., a nonconcurrent multiple baseline; p. 206). What are the benefits and problems of these designs? Child Development, 44, 547554. The replicated within-tier analysis looks to patterns of results within the other tiers. (Similar arguments can be made for comparisons across settings, persons, and other variables that might define tiers.) An important drawback of pre-experimental designs is that they are subject to numerous threats to their validity. Threats to Internal Validity in Multiple-Baseline Design Variations. If this requirement is not met and a single extraneous event could explain the pattern of data in multiple tiers, then replications of the within-tier comparison do not rule out threats to internal validity as strongly. The present article is focused on the second questionwhether systematic changes in data can be attributed to the treatment. We recommend that multiple baseline design be defined as a single-case experimental design that evaluates causal relations through multiple baseline-treatment comparisons with phase changes that are sufficiently offset in (1) real time (i.e., calendar date), (2) number of days in baseline, and (3) number of sessions in baseline. Neither the within-tier comparison, nor the across-tier comparison depends on the tiers being conducted simultaneously; both types of comparisons only require that phase changes occur after substantially different amounts of time since the beginning of baselinethat is, each tier is exposed to different amounts of maturation (i.e., days) prior to the phase change. AB Design. 66 : Discuss the advantages and disadvantages of using visual inspection of graphs rather than statistics to evaluate the significance of the results. Behavior Modification, 40(6), 852873. Third, patterns of results influence the number of tiers needed to yield definitive conclusions. 234235). The dimension of time is recognized in the requirement that phase changes be lagged in real timethat is, the date on which the phase changes are made. A coincidental event may contact a single unit of analysis (e.g., one of four participants) or multiple units (e.g., all participants). Without the latter you cannot conclude, with confidence, that the intervention alone is responsible for observed behavior changes since baseline (or probe) data are not concurrently collected on all tiers from the start of the investigation. Effects of instructional set and experimenter influence on observer reliability. Although the claims that nonconcurrent multiple baseline designs are weaker than concurrent multiple baselines, especially with respect to threats of coincidental events, are nearly universal in the current literature, none of these authors acknowledge or address, the arguments made by Watson and Workman (1981) and Hayes (1981) in support of these designs. Examples could include family events, illness, changed social interactions (e.g., breaking up with a partner), losing or gaining access to a social service program, etc. Timothy A. Slocum. Hersen, M., & Barlow, D. H. (1976). Journal of Consulting & Clinical Psychology, 49(2), 193211. Pearson. Campbell, D. T., & Stanley, J. C. (1963). Although publication dates would suggest that Kazdin and Kopel (1975) was published before Hersen and Barlow (1976), Kazdin and Kopel cite Hersen and Barlow, and not the other way around. Single-case research designs: Methods for clinical and applied settings (3rd ed.). Exceptional Children, 71, 165179. Nonconcurrent multiple baseline designs, however, do not afford this comparison. WebA multiple baseline design across behaviors was used to examine intervention effects. However, in a concurrent multiple baseline across participants, participant-level events contact only a single tier (participant)the coincidental event would not contact other tiers (participants)we might say that the across-tier analysis is inherently insensitive to detecting this kind of event. limitation of alternating treatment designs: o it is susceptible to multiple treatment interference, o rapid back-and-forth switching of treatments does not reflect the typical manner in which interventions are applied and may be viewed as artificial and undesirable. Data from the treatment phase in one tier can be compared to corresponding baseline data in another tier. Kazdin, A. E., & Kopel, S. A. They never raise the question of whether replicated within-tier comparisons are sufficient to rule out threats to internal validity and establish experimental control. Coincidental events share the characteristic that their behavioral impact is expected to be a function of particular dates. Experimental and quasi-experimental designs of research. https://doi.org/10.1177/0145445516644699, Department of Special Education & Rehabilitation Counseling, Utah State University, 2865 Old Main Hill, Logan, UT, 84322, USA, Timothy A. Slocum,Sarah E. Pinkelman,P. Raymond Joslyn&Beverly Nichols, You can also search for this author in For example, for a child who is on the cusp of walking, a month of exposure to maturational variables may result in a significant improvement in walking, but much less change in fine motor skills. Second, we briefly summarize historical methodological writing and current textbook treatment of these designs. However, critics of nonconcurrent designs have rarely (1) made a thorough and critical analysis of the potential weaknesses of across-tier comparisons in concurrent multiple baselines, or (2) evaluated the degree of experimental control that can be demonstrated by replicated within-tier comparisons. https://doi.org/10.1016/0005-7916(81)90055-0, Wolfe, K., Seaman, M. A., & Drasgow, E. (2016). The multiple baseline design was initially described by Baer et al. (1975). Oxford. WebWhat are some disadvantages of alternating treatment design? WebAnother limitation cited for single-subject designs is related to testing. This has been the sharpest point of criticism of nonconcurrent multiple baselines. First, in the replicated within-tier comparison, each tier of the design is exposed to the treatment at a different point in time. Thus, a multiple baseline with phase changes sufficiently lagged (in terms of number of sessions) provides rigorous control for this threat. Likewise, setting-level coincidental events are those that contact a single setting. Describe the retrospective and prospective research designs. This has at least two effects: first, the multiple baseline is seen as weaker than the withdrawal design because of this dependence on the across-tier analysis; and second, when nonconcurrent multiple baseline designs are introduced years later, their rigor will be understood by many methodologists in terms of control by across-tier comparisons only, without consideration of replicated within-tier comparisons. 7. write that after implementing the treatment in an initial tier, the experimenter perhaps notes little or no change in the other baselines (p. 94). Concurrent multiple baseline designs are multiple baseline designs in which the tiers are synchronized in real time. Department of Educational Psychology, Neag School of Education, University of Connecticut, Storrs, CT, 06269, USA, You can also search for this author in Webtreatment (Kazdin & Nock, 2003). To summarize, the replicated within-tier analysis with sufficient lag can rigorously control for the threat of maturation. Watson and Workman (1981) noted that the requirement that observations be taken concurrently clearly poses problems for researchers in applied settings (e.g., schools, mental health centers), since clients with the same target behavior may only infrequently be referred at the same point in time (p. 257). Having identified the criticisms of nonconcurrent multiple baseline designs, we now turn to a detailed analysis of threats to internal validity and features that can control these threats. A baseline (A) and an intervention (B) are included in a straightforward AB design psychological experiment (B). For example, instrumentation is addressed primarily through observer training, calibration, and IOA. Experimental and quasi-experimental designs for generalized causal inference. https://doi.org/10.1901/jaba.1968.1-91, Article We have no known conflict of interest to disclose. Coincidental events include divorce, changing of living situation, changes in school or work schedule, physical injury, changes in a setting such as construction, changes in coworkers or staffing, and many others. https://doi.org/10.1007/s40614-022-00326-1, DOI: https://doi.org/10.1007/s40614-022-00326-1. In addition, functionally isolating tiers (e.g., across settings) such that they are highly unlikely to be subjected to the same instances of a threat can also contribute to this goal. WebWeaknesses of multiple baseline designs: There are certain functional relations that may not be clearly understood by this design This design is time consuming and Create the graph from the data in Sheets; 3. When determining whether a multiple baseline study demonstrates experimental control, researchers examine the data within and across tiers and also consider the extent to which alternative explanations (e.g., extraneous variables or confounds) could plausibly account for the obtained data patterns. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. A broad and general impression such as these designs are relatively strong is not sufficient to guide experimental design decisions or to evaluate particular variations of multiple baseline designs. Instead, the idea that lag across phase changes includes three important dimensions and that these lags are critical for establishing experimental control and justifying strong causal conclusions should be elevated in importance. Barlow, D. H., Nock, M. K., & Hersen, M. (2009). As a result, concurrent and nonconcurrent designs are virtually identical in their control for maturation threats. Nonconcurrent designs are said to be substantially compromised with respect to internal validity and in general this limitation is ascribed to their supposed weakness in addressing threats of coincidental events (i.e., history). The use of single-subject research to identify evidence-based practice in special education. Single-case designs for educational research. Adding multiple tiers to the design allows for two types of additional comparisons to be used to evaluate, and perhaps rule out, these threats: (1) replications of baseline-treatment comparisons within subsequent tiers (i.e., horizontal analysis), and (2) comparisons across tiers (i.e., vertical analysis). Likewise, in a multiple baseline across settings, selecting settings that tend to share extraneous events would make the across-tier analysis more powerful than would selecting settings that share few common events. A : true B : false. Article Kazdin, A. E. (2021). This raises the question of how many replications are necessary to establish internal validity. Carr, J. E. (2005). Independent from Watson and Workman (1981), Hayes (1981) published a lengthy article introducing SCDs to clinical psychologists and made the point that these designs are well-suited to conducting research in clinical practice. This assumption was initially identified by Kazdin and Kopel in 1975, but its implications for the rigor of the across-tier comparison have rarely been discussed since that time. In general, in a concurrent multiple baseline design across any factor, the across-tier analysis is inherently insensitive to coincidental events that are limited to a single tier of that factor. Threats to Internal Validity in Multiple-Baseline Design Variations, https://doi.org/10.1007/s40614-022-00326-1, Concurrence on Nonconcurrence in Multiple-Baseline Designs: A Commentary on Slocum et al. One is that if a The details of situations in which this across-tier comparison is valid for ruling out threats to internal validity are more complex than they may appear. As we mentioned above, across-tier comparisons require the assumptions that coincidental events will (1) contact and (2) have similar effects on all tiers of the design. Behavioral Interventions, 33(2), 160172. - 216.238.99.111. The Nonconcurrent Multiple-Baseline Design: It is What it is and Not Something Else. Book The tutorial begins with instructions for how to create a simple multiple condition/phase (e.g., withdrawal research design) line graph. It would be an even greater concern if the treatment were an instructional program that requires several weeks or months to implement. Perspectives on Behavior Science Hayes, S. C. (1981). These variables share the key characteristic that their impact would be expected to accumulate as a function of number of experimental sessions. Pearson Education. Google Scholar, Harvey, M. T., May, M. E., & Kennedy, C. H. (2004). For example, Gast et al. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This comparison may reveal a likely maturation effect. https://doi.org/10.1037/a0029312, Watson, P. J., & Workman, E. A. Nonconcurrent multiple baseline designs and the evaluation of educational systems. If factors other than the experimenters manipulation of the independent variable could plausibly account for the obtained data patterns, experimental control has not been demonstrated and functional relations cannot be inferred. WebExtended baselines or interventions may threaten experimental control, delayed intervention may pose a risk to client or others as an ethical concern. This provides clear information about the number of sessions that precede the phase change in each tier, and therefore constitutes a strong basis for controlling the threat of testing and session experience. Predi Abab Design Essay Routledge. Routledge/Taylor & Francis Group. For example, there is less room for participant-level coincidental events if all participants reside in a single group home than if they reside in different group homes in different states. Carr (2005) invokes this prediction, verification, and replication logic, and concludes, The nonconcurrent MB design only controls for threats associated with maturation/exposure; it does not control for historical [coincidental events] threats to internal validity, as does a concurrent MB design (p. 220). Cooper, J. O., Heron, T. E., & Heward, W. L. (2020). Houghton Mifflin. Further, for both types of multiple baselines, the threat of coincidental events should be evaluated primarily based on replicated within-tier comparisons. Multiple baseline procedure. If an extraneous variable were to have a tier-specific effect, it would be falsely interpreted as a treatment effect. Second, the across-tier comparison assumes that extraneous variables will affect multiple tiers similarly. Testing and session experience encompasses features of experimental sessions (both baseline and intervention phases) other than the independent variable that could cause changes in behavior. This control assumes that the replications are sufficiently offset in real time (e.g., calendar days) to ensure that a single coincidental event could not plausibly cause the effects observed in multiple tiers. https://doi.org/10.1007/s40614-020-00263-x, Shadish, W. R., & Sullivan, K. J. (pp. Multiple baseline designs are the workhorses of single-case design (SCD) research and are the predominant design used in modern applied behavior analytic research (Coon & Rapp, 2018; Cooper et al., 2020). A researcher who puts great confidence in the across-tier comparison could falsely reject the idea that coincidental events were the cause of observed effects. https://doi.org/10.1002/bin.1510. Strategies and tactics of behavioral research. The strength of this control is a function of our certainty that no single coincidental event could have caused more than one change in the dependent variable. Use of brief experimental analyses in outpatient clinic and home settings. https://doi.org/10.1016/S0005-7894(75)80181-X, Kratochwill, T. R., Hitchcock, J., Horner, R. H., Levin, J. R., Odom, S. L., Rindskopf, D. M., & Shadish, W. R. (2013). So, similar to maturation, the across-tier comparison is sometimes able to reveal effects of testing and session experience, but it may fail to do so in some circumstances. The purposes of this article are to (1) thoroughly examine the impact that threats to internal validity can have on concurrent and nonconcurrent multiple baseline designs; (2) describe the critical features of each design type that control for threats to internal validity; and (3) offer recommendations for use and reporting of concurrent and nonconcurrent multiple baseline designs.
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