Below are some examples of situations which may create threat to experimental validity. Explain type of threat and how it may affect the results.

• You are conducting a research about gun control attitude. Mid-way through the study a local shooting incident occurs where 10 people die
• There is one-year gap between pre and post-test of an educational program
• Participants are exposed to similar test many times
• Dye to lay-off your experimental group became smaller