Module 9 Flashcards
Stratified Randomization
When a treatment variable is randomized among strata of the study population
In stratified randomization, we first stratify our study population by each variable that we consider important and then randomize participants to treatment groups within each stratum
Masked (Blinded)
When the participants do not know which treatment they are receiving.
Use of a placebo dose not automatically guarantee that patients are masked (blinded)
Double Blind
When both the participant and study investigators do not know who is receiving which treatment until the study is over.
A double blind study masks both the participants and researchers to the treatment allocation
Efficacy
Rate in those who received the control treatment - rate in those who received the intervention / rate in those who received the control treatment
Efficacy, or how well a treatment works under ideal conditions, may be differentiated from effectiveness, or who well a treatment works in real life situations
Equipoise
When there is a genuine uncertainty among medical experts about whether one medical treatment will be more beneficial than another.
Equipoise is a necessary condition to ethically randomize study participants to different treatments.
What is the main purpose of randomization?
To ensure that each study arm is as similar as possible to avoid bias from either participants, doctors, or researchers selecting which treatment they receive.
What is the main purpose of blinding?
To ensure that no one can intentionally or unintentionally influence the study results.
When should criteria for determining who should be in a randomized trial be spelled out
In writing, before the study has begun.
What are the alternatives to randomization
Case study - no comparison is made with a different group
“Results can always be proved by omitting controls”
What are the types of comparison groups
Historical controls
Simultaneous non-randomized controls
Randomized
Secular Changes
The many things other than a therapy/treatment that can change over time
What is critical to randomization
The unpredictability of the next assignment.
Randomization increases the likelihood that the groups will be comparable not only in terms of variables that we recognize and can measure, but also in terms of variables that we may not recognize, may not be able to test now, and may not be able to measure with today’s technology. Randomization does not guarantee comparability of the groups.
The main purpose of randomization is to prevent any potential selection biases on the part of the investigators from influencing the assignment of participants to different treatment groups.
What is true of randomization
If the treatment groups are large enough and the randomization procedure is free of bias, they will tend to be similar.
Stratified randomization
Stratify the study populations by each variable that we consider important and then randomize participants to treatment groups within each stratum.
Measure
Treatment Assigned
Treatment Received
Outcome - improvements
Outcome - side effects
Prognostic profile at entry (want it to be comparable)
Crossover
Planned crossover - when crossover is incorporated into the study and participants serve as their own controls. Must account for carryover and have an appropriate washout period. Psychological responses to the therapies and their sequence must be accounted for. Not possible for surgery or if the treatment cures the disease.
Unplanned crossover - contamination of the treatment arms. Offset by an intention to treat analysis. An as treatment analysis becomes a cohort study.
Factorial Design
When we test for two treatments that are independent at the same time.
Net effect of noncompliance
non-differential - it will pull the results toward the null.
Number needed to treat
1/rate in the untreated group-rate in the treated group
It represents the number of people that you would need to treat to prevent one adverse event
Presented at 95% confidence
Generalizability
External validity
Internal Validity
Determined by how the randomization was performed and when the study is free of biases and other methodological problems.
Comparative Effectiveness Research
Two or more existing interventions are compared to determine which intervention would work best in a given population for a given patient
equivalence studies
designed to determine if a less expensive intervention is as effective as the more expensive treatments
Phase 1 Trials
Clinical pharmacology studies - small studies of 20-80 people that look at safety issues with a new drug or treatment
