1.3 Vocab - Experimental Design Flashcards
What is a census?
Measurements or observations from the entire population
What are the two types of statistical studies?
Observational and experimental
What is an observational study?
Observations and measurements are conducted in such a way that doesn’t change the response or the variable being measured. No treatment - observe and measure only.
What is an experimental study?
A “treatment” is deliberately impressed on the individuals in order to observe a possible change win the response or variable being measured.
Observational or Experimental?
Researchers study the effect of vitamin D3 supplementation amount patients with antibody deficiency or frequent respiratory tract infections. To perform the study, 70 patients receive 4000 IU of vitamin D3 daily for a year. Another group of 70 patients receive a placebo for one year.
Experimental
What is the placebo effect?
Occurs when a subject receives no treatment but (incorrectly) believes he or she is in fact receiving treatment and responds favorably.
What is a completely randomized experiment?
An experiment in which a random process is used to assign each individual to one of the treatments.
What is a block?
A group of individuals sharing some common features that might affect the treatment
What is a randomized block experiment?
Individuals are first sorted into blocks, and then a random process is used to assign each individual in the block to one of the treatments.
What is a lurking variable?
Known or unknown variables that might be an underlying cause of change in response in the experimental group - outside of knowledge
What is a confounding variable?
Variable inside study without realizing it
What is randomization?
Used to assign individuals to the two treatment groups. Helps prevent bias in selecting members.
What is replication?
Repeating the experiment multiple times on many patients to reduce the possibility that the differences in pain relief for the two groups occurred by chance alone.
What is a double blind experiment?
Neither the individuals, nor the observers know which subjects are receiving the treatment. Controls bias.
What is a single blind experiment?
The observe knowns who receives treatment, but the individual does not - can have bias
- may be the best choice for gathering info across wide arrange variables
- many questions can be included
- nonresponse can introduce bias
Surveys
- second most convenient technique for gathering info on many variables
- protocols for measure t and recording need to be specified carefully
Observational studies
- most stringent and restrictive data-gathering technique
- time consuming, expensive, difficult
- number of variables may be limited
Experiments
