Field Experiment - Caveats

Caveats

• Fairness of randomization (e.g. in 'negative income tax' experiments communities may lobby for their community to get a cash transfer so the assignment is not purely random)
• Contamination of the randomization
• General equilibrium and "scaling-up"
• Difficulty of replicability (field experiments often require special access or permission, or technical detail—e.g., the instructions for precisely how to replicate a field experiment are rarely if ever available in economics)
• Limits on ability to obtain informed consent of participants
• Field testing is always less controlled than laboratory testing. This increases the variability of the types and magnitudes of stress in field testing. The resulting data, therefore, are more varied: larger standard deviation, less precision and accuracy, etc. This leads to the use of larger sample sizes for field testing.