Chapter 12 Flashcards
An experimental study (intervention study) does what?
Assigns participants to intervention and control groups in order to test whether an intervention causes an intended outcome.
What is the primary distinction between an experimental study and other study designs?
Experimental studies assign participants to receive a particular exposure.
Which three studies are observational designs? (Dont “do” anything)
1) Cross-sectional
2) Case-control
3) Cohort
Which study is the gold standard for assessing causality?
Experimental study
A typical experimental study design in the health sciences is:
A Randomized Controlled Trial (RCT)
What is a randomized controlled trial (RCT)?
1) Some participants are randomly assigned to an active intervention group
2) The remaining participants are assigned to a control group
3) All participants from both groups are followed forward in time to see who has a favorable outcome and who does not.
What is a requirement of an experimental study?
The experiment has to be ethically justifiable.
What do you have to watch out for in experimental studies?
Noncompliance
What is the key statistical measure for experimental studies?
Efficacy
All experimental studies require careful definitions of:
1) The intervention
2) What type of control is appropriate
3) How participants will be assigned to exposure groups
4) What constitutes a favorable outcome for the trial
What is the first step in an experimental study?
Carefully defining the intervention that participants assigned to the active intervention group will receive, and deciding on the person, place, and time (PPT) criteria for the study.
What should the description of the experimental study state?
1) What the intervention will be
2) The eligibility criteria for participants
3) Where and how participants will receive the intervention
4) When, how often, and for what duration participants will receive the intervention 
What are the three types of experimental trials?
1) Superiority trial
2) Noninferiority trial
3) Equivalence trial
What is a superiority trial?
Demonstrates that a new intervention is better than the control. (Must define what “better” is)
What is a non-inferiority trial?
The intervention is not worse than the control.
What is an equivalence trial?
The intervention is equal to the control.
What is the first step for defining the measures of success?
Defining a favorable outcome for an individual.
What is one commonly used type of control group in experimental studies?
Placebo
What is a placebo?
An inactive comparison that is similar to the therapy being tested.
What is the goal of a placebo-controlled study?
It allows the effect of the active therapy to be examined separately from the boost in health status that people may experience simply by participating in a clinical trial or receiving some other intervention.
Do all experimental studies use placebos?
No; if the goal is to test whether a new therapy is better than the current one, we use the current therapy as the control.
Different interventions are compared in various combinations (ex. dosage and duration) within one randomized control trial using what kind of design?
Factorial design.
Why shouldn’t experimental studies include a control group of participants who are randomly assigned to maintain their usual routines?
1) Ethically: discourages the adoption of healthier lifestyles during the course of the study.
2) Hawthorne effect bias: participants change their behavior for the better because they know they are being observed.
Which study uses the same individuals as the control group?
A before-and-after experimental study.
When do we use a before-and-after study?
When there are ethical concerns about the appropriateness of not assigning all participants to potentially life-saving intervention.
What is a before-and-after study
A non-randomized experimental study that measures the same individuals before and after an intervention.
What is the crossover design in a before-and-after study?
Some participants are first assigned to the active intervention and then the control, and others first to the control and then to the active intervention.
Why should we give both groups of the crossover design a break between the two parts of the experiment? What is the break called?
To reduce the carryover effects of the first treatment biasing the apparent results of the second treatment; washout period.
Why are the results of crossover experimental designs not as clear-cut as placebo studies?
Because time alone can lead to significant improvements or declines in health status, especially among the severely ill.
What is blinding or masking?
A type of observer bias where participants in an experimental study (and maybe some research team members) do not know whether a participant is in the active intervention group or the control group.
What is a single-blind study?
A study where participants are unaware of their exposure status.
What is a double-blind study?
A study where neither the participants, nor the people assessing the participants health status know which participants are in the active and control groups.
What kind of bias does blinding minimize?
Information bias that can occur if participants or assessors are able to evaluate outcomes differently based on the results they expect for an exposure. (observer bias if assessors)
When is a blind study only possible?
When all participants are assigned to similar exposures (ex. pill that looks the same).