Controlling Threats to Internal Validity -Participation 4

What are some other specific threats to internal validity as discussed in Neutens and Rubinson (2014), in the same chapter, 5, and what are some experimental design changes you can make to help control for those?     

Reference:

Neutens, J.J., & Rubinson, L. (2014). Research techniques for the health sciences (5th ed.). San Francisco, CA: Pearson Benjamin Cummings

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