Random Sampling and Data Collection - AP Statistics

What is the difference between qualitative and quantitative data?

Qualitative data is descriptive; quantitative data is numerical. Different analysis methods apply to each type.
What is a simple random sample?

A sample where each member has an equal chance of selection. Ensures randomness and prevents selection bias.
What is voluntary response bias?

Bias that occurs when individuals can choose to participate. Creates unrepresentative samples with extreme views.
Explain the term 'population' in statistics.

The entire group of individuals or instances about whom we hope to learn. Target group for statistical inference and conclusions.
Identify the effect of leading questions on data collection.

They can introduce response bias by influencing participants' answers. Compromises data validity and reliability.
Define confounding variable.

An external variable that affects both the independent and dependent variables. Must be controlled to establish valid causal relationships.
What is the main goal of data collection?

To gather accurate and reliable data relevant to the research question. Enables evidence-based decision making and inference.
What is a convenience sample?

Sample selected based on ease of access. Not random; prone to selection bias.
What is random assignment?

Randomly assigning subjects to treatment groups to control for confounding variables. Minimizes confounding and ensures fair comparison.
What is the role of an independent variable in an experiment?

The variable manipulated to observe its effect on the dependent variable. The factor being tested for its effect.
Identify what an outlier is in data collection.

An observation that lies an abnormal distance from other values. May indicate data errors or unusual observations.
Define sampling distribution.

The probability distribution of a given statistic based on a random sample. Foundation for statistical inference about populations.
What is an experiment in statistics?

Study where the researcher manipulates one or more variables to observe effects. Allows researchers to establish causal relationships.
What is non-response bias?

Bias introduced when responses are not obtained from all selected participants. Creates incomplete data and potential bias.
Identify the purpose of clustering in sampling.

To divide the population into clusters and randomly select entire clusters. Efficient when population naturally groups together.
Define proportional sampling.

Sampling method where the proportion of each subgroup in the sample matches the population. Maintains population structure in sample composition.
Identify the meaning of 'replication' in experiments.

Repeating an experiment to confirm results. Increases confidence in experimental results.
What is meant by 'sampling error'?

The difference between a sample statistic and the corresponding population parameter. Natural variation inherent in sampling process.
What is the significance of sample size in data collection?

Larger samples reduce sampling error and increase result reliability. Follows law of large numbers for accuracy.
What is a sampling frame?

A list of all individuals or units in the population from which the sample is drawn. Should ideally include all population members.
Identify the role of pilot studies in sampling.

Conducted to test the feasibility and improve the design of the study. Identifies problems before full-scale data collection.
What is a systematic sample?

Select every $k^{th}$ member from a list of the population. Provides systematic coverage with random starting point.
What is meant by 'blinding' in experiments?

Concealing information from participants to reduce bias. Prevents bias from participant and researcher expectations.
Define undercoverage bias.

Occurs when some members of the population are inadequately represented in the sample. Results from incomplete sampling frame coverage.
Explain response bias.

Bias that occurs when participants provide inaccurate responses. Results from measurement errors or participant dishonesty.
Identify the purpose of a control group.

To serve as a baseline for comparison with the treatment group. Enables comparison to measure treatment effects.
What is quota sampling?

Sampling method where quotas are set for different subgroups of the population. Non-random method that can introduce bias.
What is the difference between a parameter and a statistic?

Parameter describes a population; statistic describes a sample. Parameters are fixed values; statistics are calculated estimates.
What is a placebo?

An inactive substance given to the control group in an experiment. Controls for psychological effects of treatment.
Define bias in the context of sampling.

Systematic error that results in a non-representative sample. Creates unrepresentative samples and invalid conclusions.
Define a dependent variable.

The variable being measured or tested in an experiment. The outcome variable showing treatment effects.
What is a census in the context of data collection?

The collection of data from every member of the population. Expensive and time-consuming; rarely practical.
What does 'randomization' achieve in an experiment?

It controls for confounding variables and reduces bias. Essential principle for valid experimental design.
What is a double-blind experiment?

Neither the subjects nor the researchers know who receives the treatment. Eliminates bias from expectations and placebo effects.
Define multistage sampling.

Sampling method that involves multiple stages of sampling, often combining methods. Complex but efficient for large, dispersed populations.
Define random sampling error.

The error due to chance variation in selecting a random sample. Unavoidable variability in random sampling process.
What is the benefit of random sampling?

Reduces bias and ensures each member of the population has an equal chance of selection. Creates representative samples for valid inference.
What is the Hawthorne effect?

Subjects change behavior because they know they are being observed. Threatens validity of observational studies.
Define a stratified random sample.

Population divided into strata; random samples taken from each stratum. Ensures representation from each subgroup.
Define observational study.

Researcher observes subjects without manipulation. Cannot establish causation, only association.

Study these flashcards