Module 6: Sampling Flashcards
With regards to the bulls eye analogy what are the 4 rings and the 1 arrow?
Rings: outer to inner 1. Population 2. Target population 3. Accessible population 4. Sample Arrow: 1. One participant
What can be described as selecting a group of people that will be used in a study to represent the entire population?
Sampling
Differentiate between target and accessible populations:
The target population is the group of people the researcher would like to be able to generalize findings about while the accessible population are people who meet the criteria and are accessible to the researchers
What can sampling representativeness be described as?
The ability of the sample’s key traits to very closely represent those of the population. This makes the findings generalizable
Over or under representation of key variables can lead to ______ ______.
sampling bias
In which type of sampling does every member of the population have a chance to being selected to be included in a study’s sample? Selection is random.
Probability sampling
Non-probability sampling uses non-random methods of
Non-probability Sampling Strategies include: (5)
- Convenience sampling
- Snowball sampling
- Quota sampling
- Consecutive sampling
- Purposive sampling
What is considered the weakest sampling method?
Convenience sampling
Using just the population readily available may not yield results generalizable to the target population
What is snowball sampling?
Also called network sampling. Sample members, or ‘seeds’, refer people who meet a study’s eligibility criteria
What is quota sampling?
A method of sampling in which researchers identify population strata (sub-populations of the complete population) and determine how many participants from each stratum are needed.
What is consecutive sampling?
Recruiting all of the people from an accessible population who meet the eligibility criteria over a specific time interval or for a specific sample size
What type of sampling uses a researchers knowledge about a population to select participants for a study?
Purposive sampling
4 types of probability sampling strategies include:
- Simple random sampling
- Stratified random sampling
- Cluster sampling
- Systematic sampling
What is simple random sampling?
All people in a given population have some chance of being in the sample which is randomly selected
What is stratified random sampling?
Subdividing the population into homogeneous subsets or strata and then selecting elements randomly.
What type of probability sampling involves selecting large groupings (ex-nursing schools) first, typically with successive subsampling of smaller units (ex-nursing students) in a multistage approach?
Cluster sampling
What is systematic sampling?
Method using selection of every k’th case from a list resulting in an essentially random sample
What is the standard distance between sampled elements in systematic sampling called?
sampling interval
Why should quantitative studies have larger sample sized than qualitative studies?
Results will be more likely to be representative of the population, decreasing statistical error
What does the an effect size express?
The strength of relationships among research variables
What is the method used to estimate sample size needs?
Power Analysis
What are the 4 factors that affect the power of a study?
- Significance criterion (alpha)
- Population effect size (Y)
- Sample size (N)
- Power (1-beta)
What is alpha representative of in a power analysis?
0.05= 5% chance that a Type I error will occur; that the outcome occurred by chance and not as a result of the independent variable
What does the population effect size refer to in a power analysis?
The magnitude of the relationship between research variables. A statistical representation of the strength between 2 variables. This is often obtained from other similar studies conducted prior or by a pilot study
What does the power component of power analysis refer to?
Probability of obtaining a significant result and not committing a Type II error.
1 (100%, power) - 0.2 (beta, chance of committing a type II error)= 80% (desired amount of power)
What type of power analysis is conducted before a study begins?
A priori
