A city in Arizona has asked Professor Rodriguez to assess gun safety perception. Professor Rodriguez will select a random sample of residents in the city and assess their gun safety perceptions both before and after the city conducts an educational campaign on gun safety. Right after the education campaign, the media widely reports about a shooting incident. What threat to internal validity does this pose?

Internal Invalidity occurs when the outcome of an experiment is not a representation of what actual went on in the experiment due to the fact that the experiment has been affected by other internal factors which had nothing to do with the actual experiment stimulus, so the dependent variable is affected by other internal factors. Sources responsible for this are maturation, testing , instrumentations,statistical regression, selection bias,history , demoralization and experimental mortality.

A history refers to the effect of an event that had occured which may affect how people feel about something rather than being affected by the stimulus in the experiment.

Like in this case people now are going to respond to the experiments based on the incident of gun shoting that they have heard about on the media their response are now going to be affected by that incident instead of the actual experiment. So this historic event that has just occured will affect the experiment.