Primary data: Your own or group data that is collected firsthand on the day of the fieldwork.
Secondary data: Data collected from another source, which may be current or historical, and collected by someone else.
Quantitative data: Data with a numerical value.
Qualitative data: Data as words, views, or feelings.
Reliability: Where the data can be trusted to give an accurate representation.
Bias: Where your sampling does not represent the whole data set because you have selected preferred data.
Sampling: A selection of data to represent the information you want to collect, sampled in a planned way to avoid bias.
Systematic sampling: Having a system to collect samples, such as every 2m along a transect or every 5th person.
Random sampling: Using random numbers to select a sample, ensuring an unbiased selection.
Stratified sampling: Using prior knowledge to decide where you collect samples from a selected area or group.