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?