Where might bias exist in the study and for how was it controlled?

Assignment Overview: Social Psychology Research: Bias and Ethics
As a student of psychology, it is important to fully understand how research is conducted, as well as the numerous issues associated with sound research. Two important research issues are bias and ethics. When a research study is biased, either by the study design, the participants (subject bias), or the conduct of the study or interpretation of the results (experimenter bias), the results may be misleading. When practitioners then apply the results of the study to a real world situation, the impact may be ineffective, may achieve different results than expected, or may even be harmful. Unbiased research is essential.
Another important consideration in psychological research is ethics. Any research must be ethical in how it is conducted and how the results are used. A high level of ethics is especially critical when it comes to research involving human subjects, which is the case with most psychological research. Ethics in research involves honesty, objectivity, integrity, carefulness and competence, openness, respect for intellectual property, respect for privacy, confidentiality, responsible publication of findings, social responsibility, non-discrimination, legality, care of animals for those studies involving animals, and protection of the rights of human subjects.
This  Assignment asks you to analyze a social psychology research article for bias and ethics. The skills acquired can be applied to a critique of any scientific research study.
To prepare for this assignment:
•    Review Chapter 1 of the course text, Social Psychology, focusing on research bias and research ethics.
•    Watch the “Research Methods” video from the Contemporary Videos in Social Psychology DVD. Focus on the various problems that can be associated with different types of research.
•    Read the online article, “What Is Ethics in Research and Why Is It Important?” Focus on the expectations of ethics for the scientific community, how results are used in the real world, and related ethical issues.
•    Select one of the following articles from this weeks Learning Resources:
o    “Intervening to Decrease Alcohol Abuse at University Parties: Differential Reinforcement of Intoxication Level”
o    “An Attitude-Behavior Model of Salespeoples Customer Orientation”
o    “Prosocial and Antisocial Behavior in Preadolescence: Teachers and Parents Perceptions of the Behavior of Girls and Boys”
o    “The Self-Protective Altruist: Terror Management and the Ambivalent Nature of Prosocial Behavior”
o    “A Cross-Cultural Study of Environmental Motive Concerns and Their Implications for Proenvironmental Behavior”
•    Read your selected article thoroughly and think about the following questions:
What was the purpose of this research study?
How were the participants selected?
What kind of design is the study? (correlational or experimental)
How was data collected?
Where might bias exist in the study and for how was it controlled?

What might be the implications of bias in this study? In other words, if the results of this study were applied in real life and bias was indeed present, what might be the results?