Because in Europe there was a hunger, war and low level of living standards, so ppl decide to migrate to the US in search for a better life.
Answer:
Yes one should provide his/her recommender with a letter about oneself for grad school.
Answer: C. Confounding
Explanation: Confounding variable is a variable or factor which lead us to believe that there is a correlation or relationship between a two variables, However, the observed correlation or relationship is non-existent or spurious. Confounding variables are caused by external influences the outcome of experiments.
In the scenario above, a correlation doesn't exist between stress and employees ability to work, until a confounding variable 'supervisor' came in resulting in a spurious relationship between the previously measured variables.
