Probability Sampling
The most basic probability method, often described as "drawing names from a hat," where every individual in the population has an equal chance of being selected.
What is Simple Random Sampling?
This sampling method is based on the researcher's ease of access, such as surveying students who are conveniently available in the library.
What is Convenience (or Opportunity) Sampling?
This ethical principle requires that participants voluntarily agree to take part in research after being fully informed of its nature, risks, and benefits.
What is Informed Consent?
When some members of a population are systematically more likely to be selected than others, this specific form of error is introduced.
What is Sampling Bias?
The difference between a sample statistic, like the sample mean, and the true population parameter.
What is Sampling Error?
This random sampling technique involves selecting a random starting point and then choosing every nth person from a list of the population.
What is Systematic Sampling?
A non-probability method where participants are recruited through referrals from existing participants, often used for hard-to-reach populations.
What is Snowball Sampling?
Using student volunteers in a psychology department to take part in a study is a form of sampling that is fast and cheap but may produce this kind of unrepresentative sample.
What is a Convenience Sample?
When researchers can only access certain segments of a population, like people with landline phones, this specific type of bias can occur.
What is Undercoverage Bias?
A hypothetical distribution showing the results of repeatedly taking random samples of the same size from a population.
What is a Sampling Distribution?
A researcher divides the school population by grade level and then randomly selects students from each grade to ensure that each group is proportionately represented.
What is Stratified Sampling?
Researchers who post an advertisement online asking for participants are using this type of non-probability sampling.
What is Self-Selected sampling?
When relying on this type of non-probability sample, a researcher must be careful to acknowledge that the participants may possess a particular bias due to their motivation to participate.
What is Self-Selected (or Volunteer) Sampling?
Participants in a study who are motivated to be helpful and cooperative with the researcher might produce this type of demand characteristic.
What is the Good-Subject Effect?
The theorem that states that the sampling distribution of the mean will be approximately normal for large samples, regardless of the population's distribution.
What is the Central Limit Theorem?
A psychology department at a large university randomly selects three psychology classes and then studies every student in those chosen classes.
What is Cluster Sampling?
A type of non-probability sampling where a researcher ensures there is a proportional representation of certain groups by recruiting participants until a predetermined number for each group is met.
What is Quota Sampling?
Researchers must consider the potential for harm to participants, especially when using sampling methods that target these groups, such as children or individuals with certain disorders.
What are Vulnerable Populations?
This occurs when some participants fail to complete or drop out of a study, particularly in longitudinal research, which can compromise the randomness of the initial sample.
What is Attrition Bias?
This is a measure of the variability of a sample statistic, such as the sample mean, across different samples.
What is Standard Error?
This advanced form of probability sampling combines two or more techniques, such as randomly selecting school districts and then randomly selecting students within those districts.
What is Multi-Stage Sampling?
This qualitative sampling method involves the researcher continuing to recruit new participants not to increase representativeness, but to refine an emerging theory by finding cases that challenge or confirm their ideas.
What is Theoretical Sampling?
Ensuring this ethical principle is particularly important when using sampling techniques like snowballing, where a participant's identity might be revealed through their social network.
What is Maintaining Confidentiality?
When the very people who choose to participate in a study are systematically different from those who don't, this type of bias is most prevalent in studies using volunteer samples.
What is Self-Selection Bias?
This is the probability that a statistical test will detect an effect when a true effect actually exists.
What is Statistical Power?