Chapter 8: Experimental Study Designs Flashcards
Experimental Study Design?
-Manipulation of study factor: exposure timing intensity duration -randomization of study subjects: intervention receipt no receipt
What is a quasi-experimental design?
a study in which the investigator is unable to randomly allocate subjects to the conditions (interventions or control) of the study
Intervention study?
an investigation involving intentional change in some aspect of the status of the subjects. Employed to test the efficacy of of a preventative or therapeutic measure
controlled experimental studies?
involve randomization of subjects to exposures under the control of the investigator
quasi-experimental studies?
involve external control of exposure w/o randomization
Intervention designs include?
- clinical trials (focused on the person)
- community trials/intervention (focused on the community)
A clinical trial?
a research activity that involves the administration of a test regimen to humans to evaluate its efficacy or its effectiveness and safety. The term is broadly polysemic [capable of having several possible meanings]: meanings include from the first test of a drug in humans [refer to foregoing examples] without any control treatment to a
rigorously designed RANDOMIZED CONTROLLED TRIAL
-Ex: pg. 854
What’s a polyphylactic trial?
designed to evaluate the effectiveness of a substance or program
- Ex: a vaccine against measles or polio
- Ex: vitamin supplementation or patient education
What’s a therapeutic trial?
the study of a new surgical procedure or curative drugs to evaluate how well they bring about an improvement to the patient’s health
What are clinical end points?
outcomes, or results of clinical trials
Effectiveness?
the extent to which a specific intervention, procedure, regimen, or service produces a beneficial result under ideal conditions; the benefit to the person
Efficiency?
the effects or end results achieved in relation to the effort expended in terms of money, resources, and time
What is a placebo?
a nonactive medication that resembles the drug being tested in the trial
-the placebo effect is when a person may believe that a pill or treatment will heal them though that treatment (placebo) does nothing
What is a single blind design?
the subject is unaware of group assignment, although informed consent is obtained before assignment. They don’t know if they’re in the “control (placebo) group” or “treatment group”
What is a double blind design?
used to reduce the likelihood of biased assessment. neither the subject or the experimenter is aware of the group assignment (treatment or control)
What happens in Phase I of clinical trial?
Small study to evaluate the safety of a treatment for humans
What happens in Phase II of clinical trial?
Study to assess the efficacy of and safety of treatment
What happens in Phase III of clinical trial?
Large randomized study to evaluate effectiveness, monitor side effects
What happens in Phase IV of clinical trial?
Post-market study to monitor risks, benefits, and optimal use
What is fixed randomization?
once subjects have been selected, pass the eligibility determination, and agree to participate, they have an equal probability of of being assigned to the intervention or control arm
What is systematic sampling?
involves choosing every nth member member of a pop. until the desired sample size is reached
What is a stratified sample?
requires breaking the study population into subgroups and sampling from each subgroup.
What is a treatment crossover?
refers to any change of treatment for a patient in a clinical trial involving a switch in study treatments.
-Figure 8-16 (page 883)
A community trial?
an experiment which the unit of allocation to receive a preventive, therapeutic, or social intervention is an entire community or political subdivision. Intervention trials at the level of entire communities
-Figure 8-18 (page 895)
What is a cluster randomized trial?
another name for a trial that randomizes units like communities to the conditions of an intervention
-randomizes intact social units like households, hospital wards, classrooms, neighborhoods, primary care practices, etc.
What is statistical power?
the ability of the study design to detect the hypothesized outcomes of the study
Which of the following is a characteristic of an experimental study?
Exposures assigned to study subjects (usually randomly) as part of the study protocol
What is the primary advantage of setting strict inclusion criteria for a randomized clinical trial?
Improve internal validity
Subjects serve as their own control in which type of intervention study?
Cross-over
Subjects for an exposure-based cohort study would be selected most appropriately from:
Firefighters who respond to emergency calls by putting on heavy protective suit, and thus may develop fatigue during the emergency response
