Ch 14 Single-Case Exp Research Designs

Similarities to other studies

-Like a case study, single-case research focuses on a single individual and allows a detailed description of the observations and experiences related to that unique individual -Like time-series research, the single-case approach involves a series of observations made over time -Although single-case designs are similar to descriptive case studies and quasi-experimental time-series studies, the designs discussed in this chapter are capable of demonstrating cause-and-effect relationships and, therefore, are true experimental designs

Deciding When to Change Phases

-primary factor determining when a new phase should be started is the emergence of a clear pattern within the preceding phase 1. When the data in a baseline phase show a trend indicating improvement in the client's behavior, a researcher should not intervene by introducing a treatment phase -one clinical and one experimental 2. the baseline data indicate a seriously high level of dangerous or threatening behavior. -researcher probably should not wait for the full set of five or six observations necessary to establish a clear pattern. Instead, the researcher/clinician has an ethical obligation to begin treatment immediately

Characteristics of a Multiple-baseline Design

-results for a study involving two different participants, both of whom are exhibiting the same problem behavior; the top half of the figure presents data for one participant and the bottom half shows the data for the second participant. -the treatment phase is initiated for the second participant, but at a different time from that at which treatment is begun for the first participant. -Unlike other single-case designs, we should note that the multiple-baseline designs across subjects require a minimum of two participants -the multiple-baseline design can be used to evaluate the treatment of one behavior that is exhibited in two different situations

Control of other variables is achieved with a combination of three components in all single-case designs:

1. Baseline: There is a clear measure of baseline behavior prior to administering any treatment. 2. Repeated Observations: Multiple measures are obtained during baseline and each treatment condition to ensure that outside factors are not influencing behavior until the researcher intervenes and changes to the next treatment condition. The success of a single-case design requires that the series of observations/measurements during baseline and each treatment are stable 3. Replication: If the results show a clear change in behavior when the researcher changes the treatment condition, the same change must be demonstrated a second time before the researcher can conclude that the change in treatment is responsible for causing the change in behavior.

four specific characteristics of single-case data that help determine whether there is a meaningful change between phases.

1. Change in average level 2. Immediate change in level 3. Change in trend 4. Latency of change

There are three fundamental differences between single-case designs and traditional group designs.

1. The first and most obvious distinction is that single-case research is conducted with only one participant or occasionally a very small group. 2. Single-case research also tends to be much more flexible than a traditional group study. A single-case design can be modified or completely changed in the middle of a study without seriously affecting the integrity of the design, and there is no need to standardize treatment conditions across a large set of different participants. 3. Single-case designs require continuous assessment. In a traditional group design, an individual subject typically is observed and measured only once or twice. A single-case design, however, normally involves a series of 10-20 observations for each individual.

There are two general strategies for conducting a component-analysis design

1. begin with a full-treatment phase (including all the different components), then remove or withdraw components one by one to see whether the effectiveness of the treat- ment is reduced 2. begin with a baseline phase, then add components one by one to see how each individual component contributes to the effectiveness of the total treatment package. The process of adding or withdrawing components can be accomplished using either a reversal design or a multiple-baseline design.

minimizing clients, therapist, and family members to stop treatment

1. everyone can be reassured that the withdrawal of treatment is a temporary event; the treatment will be returned. 2. the eventual withdrawal of treatment is often a practical necessity. Eventually, the client must be released to return to a normal life.

To demonstrate the existence of a cause-and-effect relationship

1. manipulation 2. control

Advantages of single-Case Designs

1. single-case designs is that they allow researchers to establish cause-and-effect relationships between treatments and behaviors using only a single participant. 2. flexibility 3. that they make experimental clinical research compatible with routine clinical practice

researchers can employ several techniques to help uncover a consistent pattern.

1. the researcher can simply wait; that is, keep making observations and hope that the data will stabilize and reveal a clear pattern. 2. simply to average a set of two (or more) observations. 3. look for patterns within the inconsistency.

Disadvantages of single-Case Designs

1. these designs is that the relationship is demonstrated only for one participant 2. the requirement for multiple, continuous observations. 3. absence of statistical controls. -Problems can arise if there is any ambiguity at all in the graphed results

treatment phase

A series of treatment observations

The key component of a reversal design is a return to baseline followed by a second demonstration of the treatment effect.

A typical study would consist of the following phases: 1.Baseline phase 2.A series of phases adding treatment components one by one 3.Return to a baseline phase 4.Repeat the series of phases adding treatment components.

ABAB Design

ABAB research design can establish, with good credibility, the existence of a cause-and-effect relationship between the manipulation of a treatment and corresponding changes in behavior Limitations 1. withdrawing treatment may not result in a change in behavior. -not appropriate for evaluating treatments that are expected to have a permanent or long-lasting effect. -Degrees of failure are also possible 2. A second problem with an ABAB design concerns the ethical question of withdrawing a successful treatment. The ABAB design asks a clinician to withdraw a treatment that has been shown to be effective.

Component Analysis with a Multiple-Baseline Design

Because toilet training produces a permanent change in behavior, the researchers used a multiple-baseline across participants design to evaluate the following training components: 1. Cotton underwear instead of diapers or pull-ons. 2.A dense sit schedule, which required the child to sit on the toilet every 30 minutes. Each sit lasted 3 minutes or until success. 3.Differential reinforcement: Children were given preferred items if they were dry at underwear checks every 30 minutes or if they asked to use the potty.

statistical significance and practical significance, or clinical significance.

Practical significance means that the treatment effect is substantial and large enough to have practical application

strengths and weaknesses of the Multiple-baseline Design

Strengths -multiple-baseline design is that it eliminates the need for a reversal, or return-to-baseline, phase and, therefore, is well suited for evaluating treatment effects that are permanent or long-lasting. Weaknesses -when this design is used with a single participant to examine two or more behaviors, it can be difficult to identify similar but independent pendent behaviors. The risk is that a treatment applied to one behavior may generalize and produce changes in the second behavior -the clarity of the results can be compromised by individual differences between participants or between behaviors

Treatment observations

Treatment observations are observations made when a treatment is being administered

multiple-baseline across subjects

When a multiple-baseline design uses two separate participants

stability

When the data points form a straight line with only minor deviations, the data are said to be stable, and the pattern is easy to see. Note that the data points do not have to form a perfectly straight line to be considered stable; some variability is allowed, but it should be relatively small.

multiple-baseline design

When the initial baseline phases correspond to the same behavior in two separate situations

phase change

a manipulation of the independent variable and is accomplished by implementing a treatment, withdrawing a treatment, or changing a treatment. This process begins a new phase, during which the researcher collects a series of observations under a new set of conditions.

phase

a series of observations of the same individual under the same conditions.

Single-case experimental studies

always involve manipulation of one variable.

Single-case designs or single-subject designs

are experimental research designs that use the results from a single participant or subject to establish the existence of cause-and-effect relationships. -To qualify as experiments, these designs must include manipulation of an independent variable and control of extraneous variables to prevent alternative explanations for the research results. -a treatment (variable 1) implemented or manipulated by the researcher causes a change in the participant's responses (variable 2).

The goal of single-case research

as with other experimental designs, is to identify cause-and-effect relationships between variables

component-analysis design

consists of a series of phases in which each phase adds or subtracts one component of a complex treatment to determine how each component contributes to the overall treatment effectiveness.

reversal design

consists of a series of phases including a baseline phase fol- lowed by a treatment phase and at least one replication of a baseline followed by a treatment.

Baseline observations

observations made when no treatment is being administered. A series of baseline observations is called a baseline phase and is identified by the letter A.

level

occurs when a series of measurements are all approximately the same magnitude. In a graph, the series of data points cluster around a horizontal line.

multiple-baseline design

provides an alternative technique that eliminates the need for a return to baseline and therefore is particularly well suited for evaluating treatments with long-lasting or permanent effects.

trend

refers to a consistent increase (or a consistent decrease) in the magnitude of behavior across the series of observations that make up the phase

In single-case research

researcher must rely on the appearance of the graph to convince others that the treatment effect is significant.

statistically significant result

simply means that the observed effect, whether large or small, is very unlikely to have occurred by chance.

To establish a pattern (level or trend) within a phase and to determine the stability of the data within a phase, a phase must consist of a minimum of three observations.

the length of a phase is determined by the number of data points needed to establish a clear and stable pattern in the data.

ABAB design

the most commonly used reversal design and consists of four phases: a baseline phase, a treatment phase, a return-to-baseline phase, and a second treatment phase. The goal of the design is to demonstrate that the treatment causes changes in the participant's behavior.

Unlike other experimental methods

the results of a single-case design do not provide researchers with a set of scores from a group of participants or subjects that can be used to conduct traditional statistical tests for significance.Instead, the presentation and interpretation of results from a single-case experiment are based on visual inspection of a simple graph of the data

The purpose of a phase change

to demonstrate that adding a treatment (or removing a treatment) produces a noticeable change in behavior

multiple-baseline across behaviors

using two behaviors for a single participant