On main strategy is finding a common enemy, either foreign or domestic. Another is providing economic incentives. Another is through propaganda campaigns and false history.
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Answer:
The research method that would be able to answer the research question of Irving woould be
a Correlational Research.
Explanation:
The reason behind this is the objective of each research method. In the first place, naturalistic observation would require him to observe every study participant while he is under the influence of alcohol. In the second place, the case study would require him also to follow the events of every participant or to retrieve cases associated with it. But that would be a biased study because we wouldn't be able to measure the variables quantitatively. Archival research would be good, but he would depend on previous results that might be too old to be considered good, and they might not measure the two variables. However, if we develop correlational research we would be able to measure the two variables in real-time.
1st one because that would be domestic not foreign
