Define the key terms

1. Opportunity sampling: recruiting participants that are readily available
2. Stratified sampling: matching sample characteristics to known population ones
3. Between-participants design: using each participant once in only one group
4. Within-participants design: using each participant in every group
5. Extraneous variables: variables that may influence results but that we are not interested in

​Fill in the gaps

1. Counterbalancing is the name of the method used to control for order effects.
2. A participant whose data is quite different from the other data points could be called an outlier
3. If two friends participate in a piece of research together, it could create an issue called non-independence
4. Patchy coverage of the IV could increase the Type II errors
5. The calculation used to determine a suitable number of participants is called power analysis