Definition
Secondary data
Existing data that were collected earlier and are reused for the current investigation.
What it means
Instead of making new measurements or asking new questions, you use records that already exist—such as an official weather table, a census summary, or an earlier class survey. Check who collected the data, when they collected them, and whether they fit your new question.
Remember it
Secondary data are already there, then reused.
Example
A class compares monthly rainfall using a table published by the national weather service. The rainfall records are secondary data for the class investigation.
Watch for
Downloading, copying, or retyping an existing table does not turn its observations into primary data for your investigation.
Common mix-up
Calculating a new total or average from secondary data creates a new result, but the original observations are still secondary data.
Exact meaning
Secondary data are existing observations or measurements that were originally collected for another purpose and are later used in a new investigation.