Answer: Correlational , Experimental
Explanation:
Correlational research is defined as study in which association or link or relationship between two or more number of variable is studied that occurs naturally.In this case, experiment cannot be conducted but analyzed and observation is used for researching
Experimental research is the study based on scientific research and experiment in a controllable surrounding. Variables can be altered for extracting results, calculations are done,hypothesis is written etc.
According to the question,Dr. Allen is using correlation research method for examining relationship between variables whereas Dr. Berg is using experimental research in which he is manipulating variable to observe its impact.