1. a portion of a large group -> sample
the sample is the part that you select from a population to analyze.
2. choosing a sample so that every member has an equal chance of being chosen -> random sample
in a random sample any member of the group has the same probabilities to be selected.
3. choosing a sample from people who are under 15 years old -> biased sample
when you select based on a characteristic of the group you are running a biased sampling.
- using the responses of a small group to make conclusions about the large group. -> estimating from a sample
statistics searches to infere information about a large group using the responses from a sample
