Statistics

Data Collection Methods

Techniques used to gather information, including surveys, opinion polls, interviews, observational studies, and experiments.

Population

The entire group you want to learn about in a study.

Census

A complete count of the population, often impractical due to high costs, time, and feasibility.

Sample

A smaller, manageable portion of the population used to draw conclusions about the whole group.

Simple Random Sample (SRS)

A sampling method where everyone in the population has an equal chance of being selected.

Stratified Sampling

Divides the population into groups (strata) and samples are taken from each group to ensure representation.

Cluster Sampling

The population is divided into clusters, and entire clusters are randomly selected for the sample.

Systematic Sampling

Selecting every 'n' individual from a list, starting from a randomly chosen point.

Voluntary Response Bias

Occurs when participants self-select, often leading to results that are not representative of the population.

Convenience Sampling Bias

Results are biased because only easily reachable people are sampled.

Undercoverage

Some groups in the population are not adequately represented in the sample.

Nonresponse Bias

Bias introduced when selected individuals do not participate in the survey.

Response Bias

The way questions are asked or the presence of the interviewer can influence participants' answers.

Point Estimate

A single value derived from a sample, used to estimate a population parameter.

Sampling Variability

The natural differences in results that occur when different samples are taken from the same population.

Bias

Systematic errors that consistently skew results in a particular direction.

Generalizing Results

Extending survey findings to the whole population if the sample is representative.

Limits to Generalization

The ability to generalize is limited if the sample does not accurately reflect the entire population.

Undercoverage

Some groups in the population are excluded from the sample.

Response Bias

Influenced by how questions are phrased or who asks them.

Systematic Sampling

Easy to implement but can introduce bias if there is a pattern in the list.