Chapter 9.docx

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David Nussbaum

Chapter 9 Baseline phase 1. Typically abbreviated by using the letter A 2. Represents the period in which the intervention to be evaluated is not offered to the subject 3. During the baseline phase, repeated measurements of the dependent variable are taken or reconstructed a. These measures reflect the status of the client on the dependent variable prior to the implementation of the intervention 4. The baseline phase measurements provide two aspects of control analogous to a control group in a group design a. In a group design i. We expect the treatment group to have different scores than the control group after the intervention ii. Random assignment controls for threats to internal validity b. In a single subject design i. The subject serves as the control as the repeated baseline measurements establish the pattern of scores that we expect the intervention to change ii. Without the intervention, researchers assume that the baseline pattern of scores would continue its course iii. Repeated baseline measurements allow the researcher to discount some of the threats to the internal validity of the design Carryover effect 1. The problem with within-subjects designs 2. How having been tested under one condition affects how participants behave in another condition a. E.g. i. Practice effects ii. Fatigue effects 3. The point of intervention is to reduce or eliminate the target problem without the need for ongoing intervention a. Behavioral or cognitive behavioral treatment are based on the idea that the therapeutic effects will persist over time i. This is a concert (carryover effect) that may inhibit the use of these designs for research (since one treatment may affect how a participant reacts to another treatment in the future) Clinical replication 1. Last stage of a three sequential replication strategy used to enhance the external validity of a single subject design (generalizability) proposed by Barlow and Hersen 2. Defined as a. Combining different interventions into a clinical package to treat multiple problems b. The actual replication takes place in the same setting and with clients who have the same types of problems 3. For any replication effort to be successful, the treatment procedures must be clearly articulated, identified and followed a. Failing to adhere to the treatment procedures changes the intervention and therefore is not a true replication of the experiment Concurrent multiple baseline design 1. Basic format of a multiple baseline design a. Series of AB designs (or ABA / ABAB designs could be used) are implemented at the same time for at least three cases (clients, target problems or settings) b. Therefore data will be collected at the same time c. The unique feature of this design is that the length of the baseline phase is staggered to control for external events (history) across the three cases d. The baseline phase for the second case extends until the intervention data points for the first become more or less stable i. Similarly intervention for the third case does not begin until the data points in the intervention phase of the second case become stable e. The second and third cases act as a control for external events in the first case i. The third case acts as a control for the second case Cyclical 2. A trend that is accelerating over time with regular increases and decreases Direct replication 1. First stage of a three sequential replication strategy used to enhance the external validity of a single subject design (generalizabiity) proposed by Barlow and Hersen 2. Involves repeating the same procedures, by the same researchers, including the same providers of the treatment, in the same setting, in the same situation with different clients a. The clients however should have similar characteristics b. The strength of the findings is enhanced by having successful outcomes with other clients i. When results are inconsistent, differences in the clients can be examined to identify characteristics that may be related to success or failure Duration 1. Refers to the length of time an event or some symptoms lasts 2. Usually measured for each occurrence of the event or symptom 3. In contrast to frequency a. E.g. rather than counting the number of aggressive behaviors three times per day (frequency) you can count the length of each aggressive outburst (duration) 4. A measure of duration requires fewer episodes than do frequency counts of the target problem Frequency 1. Refers to counting the number of times a behavior occurs or the number of times people
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