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