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Explain a randomized control trial

When you take a group of volunteers, and randomly assign them to two groups.
One groups gets an intervention and the other gets a non-intervention or placebo. These two groups are compared to see if there's a difference between them overtime.


What is a confounding variable?

An alternative explanation for a relationship that has been observed


Why are RCTs good at dealing with confounding variables?

In an RCT, the confounding variable will equally affect both of the randomly split group in the RCT


What is a population?

persons, objects, or events that meet a specific set of criterias


What is a target population?

the larger population to which results of a study will be generalized to


What is an accessible population

the actual population of subjects available to be chosen for a study. (a subset of the target population)


What is a sample?

a subgroup of the accessible population which allows the results to be generalized to the population


What is a sampling bias?

the extent that sample SYSTEMATICALLY misrepresents populations. Can be conscious or unconscious


What is a sampling error?

the extent that a sample RANDOMLY misrepresents population


What are the types of sample techniques?

Probability samples and non-probability samples


What is a probability sample?

Random selection (or other known probability). Sample is considered, representative of population(although it may not be).
Can estimate sampling error


What is a non-probability sample?

Non-random samples. Generalization is difficult.
Can't estimate sampling error (should not use inferential statistics)


Types of probability sampling

Simple random sampling, systematic sampling, stratified random sampling, and cluster sampling


What is simple random sampling?

Random sampling. Everyone has an equal chance of getting in the study


What is systematic sampling?

systematically choosing samples. Ex: selecting every 10th person from a group. So you can estimate the probability of a person being in the sample


What is stratified random sampling?

specifying a number from each category in the sample.
Ex: 20 students from each grade level


What is a cluster sampling?



Types of non-probability sampling

convenience sampling, quota sampling, purposive sampling


What is convenience sampling?

when subjects are chosen on basis of availability. This is the most common form


Types of convenience sampling

- Consecutive sampling: recruit everyone to meet inclusion/exclusion criteria
- Volunteers(flyers/ads): what attributes lead subjects to volunteer & potential bias of self-selection


What is quota sampling?

Like stratified, where you select a specific amount from each category, but this is not random


What is purposive sampling?

where subjects are hand-picked by specific criteria. Ex: case series


What is an extraneous variable?

any factor not related to the purpose of the study, which may affect dependent variables.
- can become confounding variable if uncontrolled


3 essential components of experimental research

- include a control or comparison group.
- independent variable manipulated by the experimenter
- subjects are randomly assigned to groups, as opposed to naturally occurring or provider choice


What is random assignment?

each subject has an equal chance of being assigned to any group.
- helps control for extraneous variables or prognostic indicators


Random sampling is used to ____.
Random assignment is used to _____.

Generalize to a population.
Equalize two groups (controls and experimental)


What is concealing allocation?

Separating people should do the "random assignment" & data collection.
Sealed envelopes and locked cabinets


What is blinding?

To control conscious & unconscious bias in anyone involved in a study.


What is a single blind?

A case where just the measurer is blinded


What is double blind?

A case where both the measurer and patient are blinded