Experimental studies- quiz Flashcards
What happens under intervention studies?
1) The investigators influence exposure of study subjects
2) manipulation and randomization
3) two types of experimental trials fall here :
controlled trials and community trials
Why blind patients ?
1) b/c patients try to get well or please physicians.
2) minimize potential bias from a placebo effect
what are the disadvantages of an experimental study?
1) limited in application
2) not as helpful as studying etiology(cause)of disease
A randomized controlled trial in a clinical setting referred to as?
A clinical trial
what are the two types of experimental trials?
1) controlled trials
2) community trials
What is the unit of analysis in a randomized controlled trial ?
The individual
what are the advantages of randomized controlled clinical trials ?
What are the disadvantages of it ?
Advantages?
1) eliminate conscious bias due to physician/patient selection .
2) averages out unconscious bias due to unknown factor
3) Groups are “alike on avg”
Disadvantage ?
1) Ethical issues
2) interferes w/ doc/ patient relationship
what are randomized community trials ?
intervention for purpose of educational/ behavioral changes at population/group level.
Selecting outcomes (endpoint)
Primary Endpoint :
whether a new treatment is better at preventing disease-related death than the standard therapy
or
the primary endpoint for most Phase III clinical trials in HIV disease is an AIDS defining event or death.
Selection of “BEST” endpoint is often complicated.
What is the purpose of an experimental study ?
Identify clinical & public health approaches to solving public health problems ( how to prevent or treat)
What are randomized controlled trials (RTC):
Subjects get randomly assigned to groups which are:
1) study or intervention and control groups
2) receive or not receive treatment.
What are the types of randomized controlled trials ?
A prophylactic trial
Therapeutic trial
Clinical trial
What is a non-randomized study? (convenience sample)
concurrent comparison group is allocated by a non-random process
What is a natural experiment ?
unplanned events can create natural experiment.
Situations that may create appropriate circumstances for a natural experiment include policy changes, weather events, and natural disasters
What is a good choice of a comparison group?
- non contaminated by treatment
- idea- possible to blind, usually meaning placebo used.
- status quo vs. new treatment
What are the problems that come with blinding ?
- unethical
- sometimes its impossible to do : for example, can’t be done on someone who will have surgery.
- problematic to blind in drug studies, where treatment has side effects.
What is a random assignment ?
1) random assignment makes intervention and control groups look as similar as possible
2) chance is only facts that determines group assignment
3) neither patient nor physician know in advance which prevention program or therapy will be assigned
- confounding and sample size in an issue
How to measure baseline variables?
Consider measuring outcome variable: know that it can
1) change over time and that
2) disease is/ or not present at baseline
Measure various predictors of outcomes (like smoking habits) to allow for statistical adjustment
what’s a Single Blind Study?
placebo controlled study
subjects are blinded but investigator aware of who is receiving active treatment
What is the measuring baseline variables?
Demographics(age, race, gender, etc.)
other factors
First table of the report of any of the randomized trials usually compared the level of baseline characteristics in two study groups.
What happens in the randomized controlled trial ?
two groups :
A. Group 1: gets placebo
B. Group 2: gets real medicine
*Both are blinded to their
group membership.
*Once time passes, both
groups are then followed-up.
questions will be: will group do better than group 2 ?
What are the issues with non-randomized studies?
- non effective at controlling unmeasured confounding variables.
- measured confounding variables, however, may be adjusted through analytic methods.
What are group randomizations?
What will group involve?
Groups/ naturally forming clusters are randomly assigned the intervention.
- practices
- schools
- hospitals
- communities
Individuals/patients within clusters are likely to be more similar to each other compared to those in other clusters.
What is a Double Blind Study?
Neither subjects nor investigators know who is receiving active treatment
What happens in within-Group Design?
Outcome in single group is compared before and after assigned intervention.
What happens in Between- Group Design ?
Outcomes compared btw 2 / more groups receiving different levels of treatment.
Who are the participants ?
Who will be part of your inclusion/ exclusion criteria?
Inclusion criteria :✔️that the prospective subjects must have if they are to be included in the study
- broad vs specific: extent of generalization to population of interest.
Is the outcome rare?
- then recruit from population at risk.
Exclusion criteria: ❌
Define exclusion criteria that help control error :
ex. advanced cancer may be fatal before end of follow up period.
exclude those who don’t comply:
such as alcoholics, people who are planning to move out and you can’t follow up
What happens in a crossover design?
Participants may be switched between treatment groups.
What are randomized trial “ community intervention “?
Intervention designed for the purpose of educational and behavioral changes at population or group level
what are ethics in research?
1) informed consent
2) delayed control
3) clinica equipoise
4) benefit/risk
5) institutional review board
6) stoppage point
7) sequential design
what’s a placebo effect?
Effect on patient outcomes (improved/ worsened) may occur due to expectations by patients that particular intervention will have effect.
What are experimental studies for and best for ?
1) controlled experiments performed in scientific research
2) best for relatively mature questions
3) best for finding cause-effect relationships and evaluating efficacy of prevention and therapeutic interventions.
What are the three types of blinding?
Single blinding: subjects
Double blinding: investigators
Triple blind: analyses
What are the advantages of an experimental study?
1) able to experimentally manipulate exposure
2) able to make strong inferences
What is a Tripe Blind Study?
Treatment and research approaches kept a secret from subjects, investigators and analyses are completed in manner that is removed form the investigators.
