Field experiments

1. Field experiments Characteristics Sampling methods Ethical issues

2. Increasing external validity • Field experiments combine random assignment and manipulation of an independent variable with the real-world validity of a natural setting. • We control the population parameters • We can eliminate participant expectancies

3. Random selection • In laboratory studies, selection of participants is rarely fully random. • In field research, we can more closely approximate random selection.

4. Sampling methods • Probability sampling methods • Random sampling: Simple or systematic • Stratified random sampling • Cluster sampling • Non-probability sampling methods • Availability or convenience sampling • Quota sampling • Purposive sampling • Snowball sampling

5. Field experiments on public behaviors • Manipulating independent variables: • Environmentally • Interactively • Consistent experimenter behavior may be difficult • Non-participants are not a control group

6. Field experiments with existing groups • Choose a group you wish to study, such as HC faculty. • Manipulate independent variables: • environmentally • interactively

7. Ethics and field experiments • Minimize stress on participants • Protect legal and human rights • If participants do not have the opportunity to consent, APA guidelines require that risk to the participant be minimal. • Pilot studies can help you decide about risk.

8. Program evaluation • Also known as outcomes assessment or effectiveness research • Needs assessment • Program planning and implementation • Monitoring and formative assessment • Summative assessment or outcome evaluation • Feedback • Observational and quasi-experimental