Final answer:
Dr. Keyes's correlational study predicts a positive relationship between pet ownership and happiness. A third variable, such as income, could confound the results. An experimental study may not be ethical, and individuals may experience approach-approach conflict when choosing pets to adopt.
Step-by-step explanation:
Dr. Keyes is proposing a correlational study to examine the belief that owning more pets leads to greater happiness. The predicted relationship between the variables in this study suggests that as the number of pets (independent variable) increases, the level of happiness (dependent variable) will also increase. The population Dr. Keyes is studying would likely include individuals or households that have the potential to adopt pets from the local shelter.
A valid operational definition of "happiness" could be the frequency of positive emotional expressions or self-reported life satisfaction scores on a standardized scale. An example of how the third variable problem could affect this study is if individuals with higher income are both more likely to own more pets and have greater overall life satisfaction, thus confounding the relationship between pet ownership and happiness.
Conducting an experimental version of this study, where individuals are randomly assigned pets, may not be ethical as it involves obligating individuals to take on pet ownership responsibilities without their full consent or consideration of the pets' wellbeing. People may face an approach-approach conflict when adopting a pet at an animal shelter because they may be attracted to multiple animals and have to make a choice between equally desirable options.