Samping and Assignment Flashcards
Probability Sampling
Results in more representative samples
Randomization occurs at some point
Decrease in sampling error
Nonprobability Sampling
May over or under represent the population
No randomization
Increase sampling error
Is cheaper
Simple Random Sampling
Probability Sampling
- each member of pop has a number and a random number generator is used for selection
- each member has equal chance of being selected
Systematic Sampling
Probability Sampling
- every nth subject on sampling frame is used - starting point is picked with random number generator
Stratified Sampling
Probability Sampling
- Randomly select from subjects in each subgroup
- Ensures representation from each subgroup
Cluster Sampling
Probability Sampling - Randomly select from a pocket of samples 2 stages (1 selected clusters and 2 within cluster) and then randomize within cluster
Convenience Sampling
Nonprobability Sampling
- Use of already available subjects
Snowball Sampling
Nonprob Sampling
- Recruit subject that then recruits more subjects
- Used when difficult to get sample
Purposive or Judgmental Sampling
Nonprob Sampling
- Researcher chooses sample based on who they think would be appropriate
Quota Sampling
Nonprob Sampling
Judgment used to select subjects from each segment based on specific properties (20 young and 20 older)
Goal of Randomization
Eliminate bias and generate a representative sample for comparison
Random Selection
is for selecting subject to be in a study
Random Assignment
is for assigning subject to experimental groups
Individual Assignment
Dice or coin toss
Can lead to unequal group sizes
Block Assignment
Predetermine # of subjects needed for each group and assign each member a number and then select subjects based on random generator