Independent variable
intervention or condition
-Cause or influences the dependent variable.
Controlled and manipulated by the researcher
Dependent variable
outcome or response
Clinical trial
research design tests how well methods of screening, preventions, diagnosis, or tx of dx work in people
Completely randomized design
random assignment to group with unique intervention
outcomes btwn groups compared at end of trial.
- parallel design
cross over design
subject is the own control
subject gets both treatments
Factorial design
subjects experience different combination of 2 more interventions
- subjects get different combos of levels of ind variable
Pretest-posttest design control group design
- testing of randomized groups before and after treatment
posttest only design control group design
randomized groups are only tested after the intervention
repeated measures design
subjects acts as own control
subjects are tested under all conidtions
also known as within subjects design
Sequential clinical trial
Data is analyzed as it becomes available so trial can be stopped as soon as evidence is sufficient enough to show difference between treatments
Single subject design
Conclusions can be drawn from the effects of a treatment based on single patient.
-Uses repeated measurments overtime for at least two periods/pieces.
- Baseline (A) equal prior to treatment
- Intervention phase (B) after treatment
- intervention phases replicated to create design
(A-B) (A-B-A)(B-A-B)
Quasi experimental design
Research design without control group, random assignment, or both
One group pretest post test design ; Quasi experimental design
Measurements on 1 group of subjects before and after treatment.
Time = independent variable with two levels (pretest and post test)
One way repeated measures design overtime; Quasi experimental design
Measurements on 1 group made at prescribed time intervals.
Time series design;Quasi experimental design
multiple measurements made before and after treatment observed patterns or trends during pre-treatment and post treatment periods
Internal validity
Intervention causes the outcome.
what is blinding and what different types exist in order to create internal validity
Method to keep individuals knowing from which subjects have received intervention or not. Reduce bias and placebo effect
Single blind: subjects are unknowing of group assignment until end of study
Double blind:Subjects and some researchers unaware of hypothesis or group assignment until end of study
Triple blind: Subject, members of research team, and data analyzers unaware of research hypothesis group assignment until end of study
Control group; what are the two most common forms of control?
What is Matching/ pairing used for ? What is it?
What is intention to treat analysis, why is it used
All subjects are analyzed together.
This preserves original balance of subject groups through randomization.
External validity
Threats to internal validity
-Threats to internal validity: history, maturation, attrition, testing, instrumentation, regression towards the mean
What is an example of a Hawthorne effect, what is the Hawthorne effect
Tendency for individuals to change behavior in response to being watched or observed in a study
-Child acts differently, well behaved in front of observer
alternate hypothesis H1
Statement of the population parameter has value different from the null hypothesis.
The alternate hypothesis is accepted when the null hypothesis is rejected