Introduction to Research Methods and Statistics: Populations and Samples
Fundamentals of Research and Statistics in Behavioral Sciences
Gathering Information in Behavioral Research:
Research in the behavioral sciences and related fields fundamentally centers on the systematic collection and gathering of information.
Example scenario: Investigating whether college students demonstrate superior learning outcomes when reading material on printed pages versus on a computer screen requires gathering detailed information regarding students' study habits and academic performance metrics.
Information gathering routinely results in vast volumes of data across various measurement types, including:
Explicit preferences
Personality scores
Subjective opinions and attitudes
Performance indicators
Dual Purposes of Statistics:
Organization and Summarization: Statistics provide tools to organize and summarize collected data so that researchers can clearly observe what occurred within a study and effectively communicate results to the broader scientific community.
Hypothesis Testing and Conclusion Drawing: Statistics assist researchers in answering initial research questions by determining precisely what general conclusions are justified based on the specific empirical results obtained.
Accuracy and Information Integrity: Statistical procedures ensure that observations are presented and interpreted in an accurate, objective, and informative manner.
Standardization and Scientific Order:
Statistics enable researchers to bring order out of complex or chaotic raw data.
Statistical methods offer a standardized set of techniques recognized and understood universally throughout the scientific community.
Standardized analytical techniques allow researchers to read, interpret, and evaluate the work of peers with a complete understanding of how the analysis was executed and what the resulting figures signify.
Concepts of Populations in Scientific Research
Definition of a Population:
A population consists of all possible members of a designated group that an investigator wishes to study.
Behavioral research typically initiates with a overarching question regarding a specific group or multiple groups of individuals.
Examples of Target Populations and Research Questions:
Factors associated with academic dishonesty among college students (Target population: College students).
The developmental impact of lead exposure on emotional problems in school-aged children (Target population: School-aged children).
Variation in Population Size:
Populations can range from exceptionally large to extremely small depending on how the investigator explicitly specifies the boundaries of the group:
Extremely Large Populations:
The entire set of all registered voters in the United States.
College sophomores across the United States.
Coffee drinkers patronizing a major national chain of cafes.
Narrowed or Moderately Sized Populations:
People in their twenties who are registered voters in the United States.
First-time voter registrants in Burlington, Vermont.
Extremely Small Populations:
Individuals diagnosed with a specific rare disease.
Endangered species, such as the Siberian tiger, which has a population of roughly only animals.
Non-Human Populations:
A population does not need to consist of human beings. Depending on the research field, a population can be composed of:
Laboratory rats
North American corporations
Engine parts produced in an automobile factory
Any other specific set of entities under investigation
Specification Requirement:
Researchers must explicitly define and specify the exact parameters of the target population under study.
In practical research scenarios, target populations are typically far too large to evaluate in their entirety.
Concepts of Samples and Sample-Population Dynamics
Definition and Function of a Sample:
A sample is a set of individuals selected from a defined population.
Because populations are usually too large to permit the measurement of every single constituent member, researchers select a smaller, manageable subset to participate in the study.
Research procedures and measurements are limited directly to the individuals in the selected sample.
Representativeness and Random Sampling:
A sample is designed and intended to be representative of the target population from which it was drawn.
A sample must always be explicitly identified in relation to its specific target population.
Random Sampling: A foundational selection method where every individual in the population has the exact same probability of being chosen for the sample, ensuring high representativeness.
Variation in Sample Size:
Sample sizes vary significantly depending on study design, resources, and requirements:
Small sample example: A study evaluating an experimental reading program using a sample of middle school students.
Large sample example: A study evaluating a new cholesterol medication using a sample of individuals.
The Full Relationship Cycle Between Sample and Population:
The interaction between samples and populations forms a complete two-way cycle:
Formulation: The research begins with a broad question concerning an entire population.
Sampling: A representative sample is selected from the target population.
Measurement: The study is conducted, and empirical data is collected directly from the sample.
Generalization: The statistical findings derived from the sample are generalized back to the broader target population to answer the original general question.