Exam 2 Flashcards
What experimental design is not a true experiment and why?
- A quasi-experimental design
- lack randomization
- lack comparison groups
What is the gold standard of true experimental design?
Randomized Control Trial
What occurs in a true experimental design?
- Subjects are randomly assigned to at least 2 comparison groups
- Experiment enables control over most threats to internal validity and provides the strongest evidence for causal relationships
What is a completely randomized design?
- Between subject design
* Subjects assigned to groups based on a randomization process
What is a randomized block design?
- Subjects classified according to an attribute (blocking variable)
- Then randomized to treatment groups
What is a repeated-measures design?
- Within-subjects design (everyone gets same interventions)
* Subject acts as own control
How many independent variables do single-factor designs have?
*One independent variable
How many independent variables do multi-factor designs have?
*Two or more independent variables
What is a single-factor design?
- One way design
- 1 independent variable is investigated
- 1 or more dependent variables
- Looking at how many independent variables there are, not how many dependent variables there are
What occurs with a RCT with 2 groups based on random assignment?
- Pretest-posttest control groups design
- Independent groups= treatment arms
- Testing pre and post treatment
- Changes in experimental group are attributable to the treatment
- Establishes cause and effect relationship
- Change in the experimental group is the post result minus the pre result to get the overall result. The change becomes the dependent variable
What occurs in a 2-group pretest posttest design?
- Comparison group recieves a second form of the intervention
- 2 experimental groups formed by random assignment
- Control group is not feasible or ethical
- Compares new treatment with “standard care”
What is a multi-group pretest posttest control group design?
- Multiple intervention groups
* Includes a control group
What are pre-test post-test designs strong in?
*Strong in internal validity
*
How can the initial equivalence of groups be established?
*By pretest scores (important for inferring causality)
How is selection bias controlled in pretest posttest designs?
*Controlled because of random assignments
What should effect groups equally in pretest posttest designs?
*History, maturation, testing, instrumentation
How is the analysis of pretest posttest designs often done?
- Often analyzed using change scores
- difference between posttest and pretest
- Also can use analysis of covariance (ANCOVA) to compare posttest scores
- using pretest scores as covariate
What is a posttest only control group design?
- Same as pre-test posttest control group design
- EXCEPT no pre-test
- Used when dependent variables can only be assessed following treatment
- e.g. length of stay in hospital (see example pg 199)
- Used when pretest is impractical or detrimental
- Is an experimental design involving randomization and comparison groups
- Strong internal validity
- Assumes groups are equivalent prior to treatment
- works best with large samples to increase probability of “equivalency”
What occurs in a multi-factor design for independent groups?
- single factor designs have 1 independent variable (with 1 or more levels) and do not account for interactions of severable variables
- Multi-factor designs have 2 or more independent variables
What occurs in a factorial design?
- Factorial design incorporates two or more independent variables, with subjects randomly assigned to various combinations of levels of the two variables
- Two-way (two-factor) design has 2 independent variables
- Three-way (three-factor) design has 3 independent variables
What is a survey?
- A series of questions
- interview
- questionnaire (written/electronic)
- Can be used in:
- experimental studies, exploratory studies, descriptive studies
What occurs in an interview?
- Ask questions and record answers
- Structured format
- Unstructured format
What occurs in a structured interview?
- Standard set of questions
- Same questions in same order to all subjects
- Same response choices
What occurs in an unstructured interview?
- Less formal
- Open ended
- Conversational
- Often used in qualitative studies