Chapter 9- Quantitative Research Design Flashcards
Causality
Etiology (causation)
Cause of health-related phenomena usually are not deterministic, but rather probabilistic- that is, the cause increase the probability that an effect will occur.
Counterfactual
What would happen to teh same people exposed to a causal factor if they simultaneously were not exposed to the causal factor?
an effect is the difference between waht actually did happen with the exposure and what would have happened without it.
A counterfactual clearly can never be realized but it is a good model to keep in mind in desiging a study ot answer cause-probing questions.
A central task for all cause-probing research is to create reasonable approximations to this physically impossible counterfactual.
Temporal causality
a cause must precede an effect in time.
Empirical relationship (causality)
a relationship between the presumed cause and the presumed effect must exist.
No cofounders
The relationship cannot be explained as being caused by a third variable.
coherence
involves having similar evidence from multiple sources
consistency
involves having similar levels of statistical relationships in several studies
biologic plausibility
evidence from lab or basic physiologic studies that a causal pathway is credible.
Experiment- typically called Randomized Controlled Trial- RCT
Researchers are active agents- not simply observers
isolating phenomena and controlling the conditions under when they occurred
Considered the GOLD STANDARD for yielding reliale evidence about causes and effects
RCTs offer the most convincing evidence about whether one variable has a causal effect on another
the goal in most RCTs is to have an identical intervention for all people in the treatment group.
manipulation
the reserachers does something to at least some participants- there is some type of intervention
Experimenters manipulate the IV by administering a treatment (or intervention) to some people and withholding from others (C)., or by administering an alternative treatment to two or more groups.
Experimenters deliberately VARY the IV (the presumed causes) and observe the effect on the outcome (O).- which is sometimes referred to as an ENDPOINT in the medical literature
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control
the researcher introduces controls, including devising a counterfactual approximation- usually, a control group that does not receive the intervention
control group- refers to a group of participants whose performances on an outcome is used to evaluate the performance of the treatment group on the same outcome. Is a proxy for an ideal counterfactual.
may be an alternative interventions, standard methods of care, or a placebo
randominzation
the researcher assigns participants to a control or experimental condition on a random basis
intervention protocols
full nature of the intervention must be delineated in formal intervention protocols that spell out exactly what the treatment is.
Tailored interventions or patient-centered interventions (PCIs)
purpose is to ebhance treatment efficacy by taking people’s characteristics into account
Each person receives an intervention customized to certain characteristics, such as demographic traits or cognitive factors.
placebo
a pseudointervention presumed to have no therapeutic value
used to control for the nonpharm. effects of drugs, such as extra attention (?)
Placebo effects- changes in he outcome attributable to the placebo condition, because of participants expectation of benefits or harm
attention control group
used by researchers when they want to rule out the possibility that intervention effects are caused by the special attention given to those receiving the intervention, rather than by the actual treatment itself.
The idea is to separate the “active ingredients” of the treatment from the “inactive
ingredients” of special attention.
dose- response effects
different doses or intensities of treatment wherein all participants get some type of intervention, but the experimental group gets an intervention that is ricker, more intense, or longer.
wait-list control group
with delayed treatment, the control group eventualy receives the full intervention after all outcomes are asseessed
comparative effectiveness research (CER)
strives to produce evidence that is especially useful for clinical-decision making
(Testing two competing interventions ?)
Randomization- Random assignment- random allocation
assigning participants to treatment conditions at random
participants have equal chance of being assigned to any group
if people are placed in groups randomly there is no systematic bias in the groups with respect to preintervention attributes that are potential confounders that could affect outcomes.
There is no guarentee that the groups will be equal.. the smaller teh sample group the less randomization.
Matching
assigning participants to control vs experimental groups, however trying to ensure each group has similar partipiant characterisitcs
Complicated to match on more than two or tree confounding simultaneously.
Basic randomization
Flipping a coin and assigned at random to one of the two groups. 50-50 chance of being assigned to intervention group.
No restrictions- sometimes called COMPLETE RANDOMIZATION
Large imbalances can occur, especially with small sample sizes.
Not recommended with sample sizes less than 200
Simple randomization
involves starting with known sample size, then prespecifying the proportion of subjects who will be randomly allocated to different treatment conditions.
Ex; we know 15 participants, so 5 will be assigned to 3 different groups- two intervention, one no intervention.
Randomization vs. Random sampling
Randomization- is a signature of an experimental design. If participants are not randomly allocated to conditions then the design is not a true experiment
Random sampling- a method of selecting people for a study- is not a signature of an experiments. Most RCTs do not involve random sampling.
allocation concealment
prevents those who enroll participants form knowing upcoming assignments, to avoid potential biases.
baseline data
preintervention data on outcomes that should be collected before randomization to rule out any possibility that knowledge of the group assignment might distort baseline measurements.
quasi- randomization
method of allocating participates in a manner that is not strictly randoms
ex: participants may be assigned to groups on an alternative basis (qother person) or based on whether their birthday is an odd or even #.
This is not a true method of randomization.
Statified randomization
in which randomization occurs seperately for distinct groups (e.g. males, females)
permuted block randomization
in which people are allocated t o groups in small randomly sized blocks to ensuer a balances distribution in each block
urn randomization
in which group balance is continuously monitored and the allocation probability is adjusted when an imbalance occurs
