4. Statistics and society, data collection and sampling Study guide 4. Statistics and society, data collection and sampling

Statistical inquiry Statistical inquiry is a process of gathering statistics that involves six steps: Pose questions. Collect the data. Organise the data. Summarise and display the data. Analyse the data. Write a report. HSC Hint – Information gained from a statistical inquiry depends on the accuracy of the data.

Quantitative data Quantitative data is numerical data. It is data that has been measured. Quantitative data is classified as discrete or continuous. Discrete – data that can only take exact numerical values such as 0 or 1. Continuous – data that can take any numerical value such as 71.25. HSC Hint – Counting a quantity often results in discrete data.

Categorical data Categorical data is data that can be divided into categories. It uses labels not numbers. Categorical data is further classified as nominal or ordinal. Nominal – name does not indicate order such as gender (M or F). Ordinal – name does indicate order such as ‘A’ for excellent, ‘B’ for good. HSC Hint – Categorical data has no quantity or amount associated with each category.

Sample types Random sample – members of the population have an equal chance of being selected. Stratified sample – categories of a population are chosen such as male/female. The members are randomly selected from each category. Systematic sample – population is divided into a structured sample size. The members are orderly selected from this structure such as each 3rd person in alphabetical order. HSC Hint – Systematic sample results in a gap between each selection.

Designing a questionnaire A questionnaire or survey is a series of questions to gather specific information. To design a questionnaire Use simple language. Make questions unambiguous. Respect the privacy of the interviewee. Ensure the questionnaire is free from bias. HSC Hint – Multiple-choice questions restrict the answers available to the respondents.