Types of Statistical Studies Notes

\begin{definition}[Statistical Study] A statistical study is a systematic investigation designed to collect, analyze, and interpret data in order to answer questions or test hypotheses about a population. \end{definition}

There are three main types of statistical studies:

1. Surveys
2. Observational Studies
3. Experiments

Each type of study has its own advantages and limitations, and the choice of study depends on the research question and the resources available.

Surveys

\begin{definition}[Survey] A survey is a method of collecting data by asking questions to a sample of individuals from a population. \end{definition}

Surveys are used to gather information about:

• Opinions
• Preferences
• Behaviors
• Characteristics of a population

• Designing a Survey

• When designing a survey, it is important to consider:
  1. The questions to be asked
  2. The sample of individuals to be surveyed
  3. The method of data collection (e.g., online, phone, in-person)

• Bias in Surveys

• \begin{definition}[Bias] Bias is a systematic error that leads to inaccurate or misleading results in a statistical study. \end{definition}
• Surveys can be affected by various types of bias, including:
  1. Selection Bias: Occurs when the sample is not representative of the population.
  2. Response Bias: Occurs when the wording of the questions influences the responses.
  3. Non-Response Bias: Occurs when a significant portion of the selected sample does not respond.

• Observational Studies

• \begin{definition}[Observational Study] An observational study is a type of statistical study where the researcher observes and records data without interfering with the subjects or controlling any variables. \end{definition}
• Observational studies are used to:
  • Identify patterns and relationships between variables
  • Make inferences about a population

• Bias in Observational Studies

• Observational studies can also be affected by bias, including:
  1. Selection Bias: Occurs when the subjects are not randomly selected.
  2. Observer Bias: Occurs when the researcher's expectations influence the observations.

• Experiments

• \begin{definition}[Experiment] An experiment is a type of statistical study where the researcher manipulates one or more variables (called treatments) to observe the effects on other variables. \end{definition}
• Experiments are used to:
  • Establish cause-and-effect relationships
  • Test hypotheses about the effects of treatments

• Designing an Experiment

• When designing an experiment, it is important to consider:
  1. The treatments to be applied
  2. The subjects to be included in the study
  3. The method of assigning subjects to treatments (e.g., random assignment)

• Bias in Experiments

• Experiments can be affected by bias, including:
  1. Selection Bias: Occurs when the subjects are not randomly assigned to treatments.
  2. Observer Bias: Occurs when the researcher's expectations influence the results.
  3. Placebo Effect: Occurs when subjects experience changes due to their expectations rather than the treatment.

• Reducing Bias in Statistical Studies

• To reduce bias in statistical studies, researchers can:
  1. Use random sampling and random assignment to ensure representativeness.
  2. Use blinding or double-blinding techniques to prevent observer bias.
  3. Carefully design questions and procedures to avoid influencing the results.