Populations and samples Flashcards
Define populations and samples Explain why samples are needed Explain the role of populations and samples in hypothesis tests Describe the links between variation, representativeness and sampling error Explain how sample size (N) and sampling strategy influence sampling error Identify and describe 3 sampling strategies Discuss the considerations involved in choosing an appropriate sampling strategy for a particular research question and population
Define population
Set of individuals with the particular characteristics under investigation in a research question
Define samples
The process of selecting some individuals from the population to take part in the study
Why are samples needed
We don’t always have access to every individual in a population, we don’t have the resources to conduct a study with everyone, we don’t have the time to conduct a study with an entire population
Define sampling error
Likely discrepancy between the results found in a particular sample and the results that would have been obtained in the population
Define sampling strategy
The approach taken to identify and recruit individuals from the population to take part in the study
When is a sample representative
When it includes all the characteristics of the population it is unbiased.
How does sample size effect sampling error
Large samples are more likely to be representative as there’s more chance of obtaining the full range of characteristics. It has a lower sampling error
How does sample strategy effect sampling error
Random sampling is more likely to be representative as there’s less chance of any systematic bias. It has a lower sampling error
What is random sampling
Researcher identifies specific individuals to recruit by randomly selecting them from a list of the entire population
What is stratified sampling
Researcher identifies specific individuals to recruit by randomly choosing them from relevant subgroups in the population with the same representation in sample as in population
Opportunity / convenience sampling
Researcher advertises the study in a specific context, individuals self-select to participate.
What are the pros and cons of stratified and random sampling
Pros: representative
Cons: High cost, need contact details of the whole population, stratified needs info on the subgroups too
What are the pros and cons of opportunity sampling
Pros: lower cost
Cons: may not be representative
