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15 Cards in this Set
- Front
- Back
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MTD |
- Enables researcher to compare relative effects of TWO or MORE interventions on a SINGLE target behaviour - intervention repeatedly reversed in successive experimental phases in order to document intervention effects - can have B or no B but can only compare baseline to the intervention right adjacent to it |
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MTD cont'd |
- one intervention is more effective than the other when it consistently has a differential effect on the target behaviour - intv reversed at LEAST twice during the study -used when comparing effects of two or more intervention on target behaviours that are REVERSIBLE- those likely to return to pre treatment levels when an intervention is removed or withdrawn |
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works on |
- behaviours that are reversible when intervention removed- eg. task behaviours, social interactions, self stimulatory behaviours, postural alignment -DOESN'T work on non-reversible bx- reading, math, communication |
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Two common threats to internal validity 1. Sequence Effects |
- result from the order in which intervention are presented to the participant -counter balance the introduction of the intervention across participants |
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2. Carry over Effects |
- impact that one intervention may have on the effectiveness of the other - effects of one intervention may carry over to the next experimental phase |
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Contrast Vs. Induction Effects |
Contrast: implementation of one intervention leads to a reduction in the effectiveness of the second intervention Induction: one intervention improves the effectiveness of the second intervention |
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Implementing an MTD study A) Replicate intervention Effects |
- Must repeatedly reverse the implementation of the interventions - 1 intervention considered more effective than the other if its effect on target bx is replicated across the adjacent experimental -effects of intervention replicated across at least THREE different conditions - |
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B) Develop an Intervention Schedule to control for Sequence Effects |
- counter balance the introduction of the intervention across participants/ bx/setting
- eg. implement social reinforcement first followed by self monitoring with participants 1 and 3, then opposite for participants 2 and 4 -reduces likelihood that the order in which intervention are implemented leads to changes in the target bx |
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C) Ensure procedural Equivalence |
- only interventions should be changed, other variables held constant
- without those controls difficult to determine wether changes in target bx occurred because of intervention or other factors - key to define the procedures -procedural equivalence on amount of tim they receive intervention, who implements them, where they are implemented, when they are implemented. - intervention script |
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D) Ensuring Fidelity of Treatment |
- should assess fidelity during 25% of all treatment sessions for each intervention |
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Design Variations ABACABCBC |
- reversal baseline phase with each intervention prior to reversing the intervention phases - withdrawal phases to compare interventions with baseline- then repeated reversals of the intervention - allow to contrast participants performance each time with baseline |
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AB BC C BC |
- compares the effects of single intervention with various packages of interventions
- potentially combining the two interventions might have an effect B or C compared with BC |
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ABAB BC B BC |
- first two reversals of the baseline and intervention are structured to establish unique impact of the intervention on target bx - BC would be reversed with B to assess impact of the second variable on the effectiveness of intervention |
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Pro's MTD |
1. used to compare the impact of multiple interventions 2. allow for more immediate implementation of the intervention or treatment |
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Con's |
1. not appropriate for establishing NEW, non reversible behaviours 2. repeated reversal of the treatments or conditions may not mesh with the typical structure of schools 3. requires researcher control for sequence and carry over effects |
