Exam 2 Quantitative Sampling Flashcards
Population
group meeting a specific description
Target population
everyone who meets the criteria (very specific criteria for study)
accessible population
those who meet the criteria and who can be accessed by the researcher (who researcher has access to)
Sample
selected portion of group you are studying
-small, specifically selected to be in study
Elements
individual or basic units to be studied
subjects/participants
human elements to be studied
Sampling plan
how you will select the sample (number, eligibility, process) written description
What is representativeness?
the sample looks enough like the population to be able to GENERALIZE the sample findings to others in the population
How must the sample similar to the population
on important characteristics
Inclusion criteria
characteristics that the subject MUST possess to be in the study.
Based on notable characteristics of the target population
Exclusion criteria
characteristics that the subject MUST NOT possess
reduces questions about impact of extraneous variables on the results
sampling bias
over or under selection of subjects on any of the significant variables
sampling error
errors made in the conclusions because of sampling bias
Clinically relevant findings
Overall picture must be one closely resembling
Probability sampling
Every element(person) in the accessible population has an equal chance of being selected for inclusion in the study
3 conditions:
accessible population must be identifiable (must be able to make a list)
All elements in the accessible population must be listed (sampling frame)
Elements are chosen by random selection
Selection method is determined by:
research purpose, question, and design
Types:
simple, stratified, cluster, and systematic random sampling
Randomization
outcome of random sampling methods
What does randomization reduce threat of?
selection bias
Less selection bias
ensures a greater likeness between the sample and the target population on the focal characteristics
Common methods:
- Draw names out of a hat
- Use a table of random numbers
- Flip a coin-heads in, tails out
- Throw dice-anyone getting an even number is in, odd number is out