Collecting and classifying data
Specify survey targets and categories and examine data types and sampling limits.
Meaning
Data collection identifies the relevant subjects and observes them using consistent criteria. The population is the whole group of interest; a sample is the part actually examined.
Example
To study commuting times for all students at a school, students are randomly selected from each grade. All students form the population, while those surveyed form the sample. Selecting within every grade reduces the risk of omitting a grade whose commuting conditions may differ. For a school-wide mean, also account for grade sizes and any differences in selection probabilities. Surveying only convenient participants may leave groups out. A large amount of data does not automatically remove selection bias.
Practice for this concept
Scope and references
Topics
Survey targets, classification criteria, categorical and numerical data, populations and samples
Learning goal
Specify survey targets and categories and examine data types and sampling limits.
Helpful background
Check what was collected, from whom, and by which classification criteria.
Collecting and classifying data
These choice exercises calculate or judge specified finite data, trials, or assumptions. They do not establish data collection, written inference, model validation, or mastery of the whole statistics area.