Chapter 5

Sampling

A systematic process of selecting a subset of individuals from a larger population to analyze and make inferences about the whole group.

Population

The entire group about which a researcher wants to make inferences.

Sample

A subset of individuals from the population selected for study.

Sampling Frame

The actual list from which a sample is drawn, ideally including every element of the target population.

Elements

The individuals or objects being studied.

Units of Analysis

The level at which data is collected (e.g., individuals, groups, cities).

Probability Sampling

Sampling methods where each element has a known and nonzero chance of selection, ensuring randomness.

Simple Random Sampling (SRS)

Every element in the population has an equal probability of being selected.

Systematic Sampling

Every nth element is selected after randomly choosing a starting point.

Stratified Sampling

Population is divided into strata, and samples are drawn separately from each group.

Cluster Sampling

Researchers divide the population into clusters and randomly select whole clusters for study.

Non-Probability Sampling

Sampling methods that are non-random and often used in exploratory or qualitative research.

Convenience Sampling

Selecting participants based on ease of access, which carries a risk of selection bias.

Purposive Sampling

Deliberate selection of participants based on researcher judgment.

Snowball Sampling

Existing participants refer new participants, forming a chain, often used for hard-to-reach populations.

Quota Sampling

Researchers set quotas to match population characteristics, leading to potential hidden biases.

Sampling Error

The difference between sample results and the true population characteristics due to chance.

Coverage Error

Occurs when the sampling frame misses key segments of the population.

Nonresponse Bias

Occurs when certain groups systematically refuse to participate in a study.

Sampling Distributions

The theoretical distribution of sample statistics if multiple samples were taken.

Standard Error

Measures variability between different samples from the same population.

Confidence Intervals

A range within which the true population parameter likely falls.

Police Use of Force Studies

Research that requires proper sampling to ensure representative data on excessive force cases.

Crime Victimization Surveys

Studies where probability sampling is essential for reliable victimization rate estimates.

Randomized Controlled Trials (RCTs)

Research designs that use probability sampling to compare outcomes before and after interventions.

What is condensation in the water cycle?

Condensation is the process by which water vapor cools and changes back into liquid water, forming clouds.

What is precipitation in the water cycle?

Precipitation is any form of water, liquid or solid, that falls from the atmosphere to the Earth's surface, such as rain, snow, sleet, or hail.

What is collection in the water cycle?

Collection is the process where water gathers in bodies of water like rivers, lakes, and oceans after precipitation.

What is the role of the sun in the water cycle?

The sun provides the energy necessary for evaporation, which initiates the water cycle by converting liquid water into vapor.