Population and Sampling in Research

Population, Sample, and Generalizability

• A population is a group of people researchers are interested in studying.
• A sample is drawn from the population to ensure it represents that population. Larger samples are better for representing the population. Samples are usually only one for a each study.
• Random assignment ensures each participant in a sample has an equal chance of being selected for a specific condition in a study.
• Random selection means each member of the population has an equal chance of being in the study.

Sampling Issues

• Sampling bias occurs when the sample chosen is not representative of the population, impacting the ability to generalize findings. How the sample is obtained is very important.
• Sampling population involves clearly defining and identifying everyone in the population.
• Sampling frame lists the people who can be invited into the study.
• Response rate reflects the number of participants who complete the study, which can influence the sample's representativeness. Participants who fail to complete a study might not be representative of the total.
• Convenience sampling is selecting participants based on availability.
• There are concerns that samples collected in this way may not represent the wider population.

Research Types and Sampling

• Basic research aims for theoretical understanding, whereas applied research targets problem-solving.
• Random selection is crucial for generalizing results to a larger population.
• Probability sampling methods (simple random, stratified, and cluster) use randomization.
• Non-probability sampling methods (convenience, purposive, and quota) rely on subjective selection criteria.

Generalizability in Psychology

• Convenience samples are common in psychology, but their generalizability may be limited.
• Researchers need to consider whether these samples are representative of larger populations.
• Basic research needs good reasons for using convenience samples, and the results should be replicated.
• Ethical issues related to samples are important for ensuring justice and fairness in research.

Generalizability Issues and Solutions

• Problems with generalizability often arise from sampling methods used in research. Solutions include collecting data from different populations, doing replications of studies, examining the differences among sexes and genders, etc.
• Statistical analysis is often used to assess whether collected samples are generalizable. Additional considerations like cross-cultural studies can improve the potential for generalizability.
• Replication is a crucial part of ensuring that findings in one study can be generalized to other studies, increasing the reliability and generalizability of research. Direct and conceptual replication methods are useful for addressing this.
• The choice of sampling technique influences the ability to generalize research findings to broader contexts.

Ecological Validity

• Ecological validity refers to the extent to which findings from a study can be generalized to real-world situations.
• Real-world studies may offer higher validity but may be hard to do.
• Studies in controlled environments might be easier to run but may offer lower ecological validity.