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What is the difference between probability and nonprobability sampling?
Probability sampling is the likelihood of any one member of the population being selected is known.
Nonprobability sampling is the likelihood of selecting any one member from the population is not known.
Why are probability sampling strategies the most commonly used?
Because the selection of participants is determined by chance. Therefore, the chance that the sample will truly represent the population is increased.
What is Simple Random Sampling?
-It is the most common type of Probability sampling procedure.
-Each member of the population has an equal and independent chance of being selected to be part of the sample.
What is the SRS's four step process?
- 1- Definition of the population from which you want to select the sample
- 2- Listing of all the members of the population
- 3- Assignment of numbers to each member of the population
- 4- Use of a criterion to select the sample you want
What is a table of random numbers?
-Is the most unbiased tool you can use to select participants from a population.
What is the general rule in Sampling?
To use a criterion that is unrelated to that which you are studying.
ex. if you are doing a study on volunteering, you do not want to ask for volunteers!
What is Systematic Sampling?
-It reduces the chances of certain participants being selected; therefore, it is less unbiased than simple random sampling.
-It is a preferred technique because it is easier and less trouble than random sampling yet less precise.
What is Stratified Sampling?
Process of selecting a sample that represents different groups or levels of a population.
-It is used to ensure that the strata (or layers; ex. race, gender etc) in the population are fairly represented in the sample.
What is stratified random sampling?
-A random sampling procedure used when subjects are known to be unequal on some variable in the population.
What is Cluster Sampling?
-Units of individuals are selected rather than individuals themselves.
-It is a great time saver but be sure that the units are homogeneous enough such that any differences in the unit itself might not contribute to a bias.
What are 2 types of Nonprobability Sampling Strategies and what are those strategies?
: based on convenience
- 2- Quota Sampling: Selects people with the characteristics you want (such as first grade, rural children) but does not randomly select from the population.
- -However, a specified number is set to be selected and once that number is met, no further selection occurs.