Special circumstances design

Research Designs for Special Circumstances

• True experiments are basic designs with high internal validity, where the independent variable (IV) is the sole cause of the dependent variable (DV).
• Key components of causality include temporal precedence (cause precedes effect), covariation of cause and effect, and elimination of alternative explanations.
• Basic experimental designs are sometimes unsuitable for research, thus solutions are needed.
• Single-case designs are useful for studying one participant.
• Quasi-experimental designs are used when random assignment isn't feasible. These designs can measure variables like race or age.
• Program evaluations assess programs aimed at positive effects on groups.
• True experiments face practical limitations in some research areas.

Program Evaluation

• Program evaluation aims to research programs designed for positive group effects.

Single-Case Experimental Designs

• These designs focus on single participants.
• They are useful for studying therapy or intervention effectiveness.
• A baseline phase, where the environment does not change is part of the design.

Solutions for Enhanced Causality

• Reversal designs provide a way to confirm findings by repeating baseline phases.
• Multiple baseline designs introduce replication in single-case designs.

Developmental Research Designs

• Developmental designs study age effects and how they relate to other variables.
• Age effects are main variables in research, illustrating how factors change with age.
• Cohort effects are unique experiences of a particular generation.
• Time-of-measurement effects occur due to socio-cultural or environmental influences on collected data.. These confound age effects.
• Developmental research lacks ability for random assignment of age.
• Cross-sectional methods study participants of various ages at one time.
• Longitudinal methods use same participants over time.
• Sequential methods use multiple cohorts (different participant groups) and time points of measurement to observe changes.

Quasi-Experimental Designs

• Quasi-experimental designs are used when true experiments are not possible or ethical (cannot manipulate IV).
• These designs cannot establish causality, due to the absence of random assignment and controlled conditions.
• Quasi-experimental designs help to identify potential weaknesses in studies that claim to be true experiments.

One-Group Posttest-Only Design

• The design exposes a group to one condition, then measures the dependent variable (DV).
• No comparison is made to other groups. The effect of the condition on the DV is unknown.

One-Group Pretest-Posttest Design

• The design gathers a pretest measure, before exposure to the condition, and then a post-test. Comparison with a "no treatment" condition provides a baseline measure to evaluate change.

Threats to Internal Validity

• Maturation threats occur when development occurs naturally over time.
• History threats include outside events that influence the study.
• Testing threats refer to the influence of repeated testing on participants.
• Instrument decay occurs if measuring instrument decreases in accuracy over time.
• Regression toward the mean occurs when participants are selected for extreme scores; changes tend to move towards the average/mean for the variable.

Continued Quasi-Experimental Designs

• Non-equivalent control group posttest-only design involves two non-equivalent groups which are exposed to different treatments, and then are compared using the DV value.
• Non-equivalent control group pretest-posttest designs follow a similar pattern to the above design. However, the comparison is made based on pretest and posttest score of the DVs.

Multiple Repeated Measures

• Multiple repeated measures designs lack random assignment, making it impossible to isolate IV effects.
• Interrupted time-series designs involve applying a treatment and measuring outcomes through time.