Suppose a single random sample of workers in a factory is exposed to five different reward systems in succession, with each system being used for one month. What is the name of the threat that reminds researchers that the research results for the last reward system may not generalize to the population of workers?

Multiple treatment interference.

Explanation:

Multiple treatment interference is the name of the threat that reminds researchers that the research results for the last reward system may not generalize to the population of workers. This is because of multiple treatment interference threatens the internal validity of an experimental or quasi-experimental design. There is difficulty in assigning variance to one of the reward systems.