Research Methods - Chapter 12
100
An ideal screening or diagnostic test would have ___% values for sensitivity and specificity
stratified randomization
the division of a population into subgroups prior to randomly but systematically assigning each individual within each subgroup to one of the exposure groups in an experimental study
number needed to harm (NNH)
the number of people who would need to receive a particular treatment in order to expect that one of those people would have a particular adverse outcome -A large NNH indicates a safer intervention
efficiency
an evaluation of the cost-effectiveness of an intervention that is based on both its effectiveness and resource considerations
quasi-experimental design
an experimental study that assigns participants to an intervention or control group using a non-random method
single-blind
participants do not know whether they are in an active group or a control group
intervention
The first step in an experimental study is to carefully define the __________ that participants assigned to the active intervention group will receive and to decide on the person, place, and time (PPT) criteria for the study
experimental
_____ studies are the gold standard for assessing causality
efficacy
a measure of the success of an intervention that is calculated as the proportion of individuals in the control group who experienced an unfavorable outcome but could have expected to have a favorable outcome if they had been assigned to the active group instead of the control group
adverse event
a negative outcome that may be the direct result of a study-related exposure or may be a coincidental occurrence that is not directly related to the study but happens after an individual receives a study-related exposure
adverse reaction
a negative side effect of a medication, vaccination, or other exposure, or another bad outcome related to a study
before-and-after study
a non-randomized experimental study that measures the same individuals before and after an intervention so that each participant's "before" status can serve as that individual's control
natural experiment
a research study in which the independent variable is not manipulated by the researcher but instead changes due to external forces
intervention
a strategic action intended to improve individual and/or population health status
Hawthorne effect
a type of bias that occurs when participants in a study change their behavior for the better because they know they are being observed
screening
a type of secondary prevention in which all members of a well-defined group of people are encouraged to be tested for a disease based on evidence that members of the population are at risk for the disease and early intervention improves health outcomes
cutpoint (treshold)
a value that divides a numeric variable into separate categories
equivalence trial
aims to demonstrate that a new intervention is as good as some type of comparison the intervention is equal to the comparison
superiority trial
aims to demonstrate that a new intervention is better than some type of comparison, not merely as good as the comparison the intervention is better than the comparison
non-inferiority trial
aims to demonstrate that a new intervention is no worse than some type of comparison the intervention is not worse than the comparison
block randomization
an allocation method that randomly assigns groups of people to an intervention group and other groups of people to a control group
standard of care
an existing therapy that is used as a comparison for a new therapy being experimentally tested
controlled trial
an experiment in which some of the participants are assigned to an intervention group and some are assigned to a non-active comparison group
blinding
an experimental design element that keeps participants (and sometimes some members of the research team) from knowing whether a participant is in the active intervention group or the control group
placebo
an inactive comparison that is similar to the therapy being tested
informational bias
bias in an epidemiological study that arises due to systematic measurement error
effectiveness
calculated with the same equation as efficacy, but refers to results obtained under real-world, less-than-ideal conditions
treatment-received analysis
experimental data includes only the participants who were fully compliant with their assigned intervention or comparison protocol -Used for calculating efficacy
equipoise
experimental research should be conducted only when there is genuine uncertainty about which treatment will work better
-The intervention -The type of control that will be used and why it is appropriate -How participants will be assigned to exposure groups -The end point that will constitute a favorable outcome for the trial
experimental study designs require careful definitions of what four things?
treatment-assigned analysis
includes all participants, even if they were not fully compliant with their assigned protocol -Used for calculating effectiveness
detection bias
information bias that occurs when a population group that is routinely screened for adverse health conditions incorrectly appears to have a higher-than-typical rate of disease because more frequent testing enables a higher case detection rate in that population than in the general population
observer bias
information bias that occurs when an observer intentionally or unintentionally evaluates participants differently based on their group membership
reporting bias
information bias that occurs when members of one study group systematically underreport an exposure or outcome
allocation bias
might occur as a result of non-random assignment of participants to experimental study groups, such as when people with different exposure histories are not equally distributed across treatment arms
parallel design
participants are randomly assigned to a particular treatment group and remain on that treatment throughout the study
crossover design
participants may be switched between treatment groups
gold standard reference test
shows the actual presence of disease in affected people
randomization
the assignment of participants to an exposure group in an experimental study using a chance-based method that minimizes several types of possible bias
Number needed to treat (NNT)
the expected number of people who would have to receive a treatment to prevent an unfavorable outcome in one of those people (or, alternately stated, to achieve a favorable outcome in one person) -A small NNT indicates a more effective intervention
diagnostic accuracy
the percentage of individuals who are correctly classified by a test as true positives or true negatives (that is, the percentage for which both the reference test and the new test yield the same result) -An ideal test will have 100% diagnostic accuracy
sensitivity
the proportion of people who actually have a disease (according to the reference standard) who test positive using the new test
specificity
the proportion of people who do not have the disease who test negative with the new test
negative predictive value (NPV)
the proportion of people who test negative who actually do not have the disease
Positive Predictive Value (PPV)
the proportion of people who test positive with the new test who actually have the disease (according to the reference standard)
carryover effects
the residual effects from the first part of an experimental study that may bias the results of the second part of a crossover study if a sufficient washout period between the two arms of the study is not implemented
prevention science
the scientific study of which preventive health interventions are effective in various populations, how successful the interventions are, and how well they can be scaled up for widespread implementation
reference standard
the test used for comparison when examining the validity of a new diagnostic test
simple randomization
the use of a coin toss, a random number generator, or some other simple mechanism to randomly assign each individual in an experimental study to one of the exposure groups
ethical challenges
Experimental studies also require careful consideration of the _____ ______ associated with assigning participants to an exposure
assigns
Experimental studies involve a particularly high level of ethical risk because the researcher _______ participants to exposures that the participants do not choose and may have been unlikely to encounter had they not volunteered to participate in a research project
favorable outcome
Because the term "better" can be defined in so many ways, the researcher must carefully define what constitutes a ______ ______ for an individual participant and for the experimental study as a whole
double-blind
neither the participants nor the people assessing the participants' health status know which participants are in an active or control group
crossover design
randomly assigns some participants to receive the active intervention first and then the control, and assigns the others to receive the control first and then the active intervention
factorial design
tests several different interventions in various combinations within one trial
randomized controlled trial (RCT)
some participants are randomly assigned to an active intervention group, the remaining participants are assigned to a control group, and all participants from both groups are followed forward in time to see who has a favorable outcome and who does not
ethically justifiable
what is a requirement for experimental study?
efficacy
what is the key statistical measure in an experimental study?
to compare outcomes in participants assigned to an intervention or control group
what is the objective of an experimental study?
does the exposure cause the outcome?
what is the primary study question of
noncompliance
what to watch out for in experimental study
washout period
when patients receive no treatment
assessing causality
when should you use an experimental study?
similar participants are randomly assigned to an intervention or control group
who is the population in an experimental study?
