Answer to Question 1
Age effects in research are usually represented as chronological age. However, age effects are due to biological, psychological, and sociocultural changes in individuals. These are not dependent upon age, per se. Cohort effects are specific to the generation to which one belongs. A cohort can consist of people born in a certain year or of people who lived during a normative historical event, such as during 9/11. Time- of-measurement effects have to do with the larger societal events happening at the time of data collection. For example, people's views of a president may vary depending upon the state of the economy.
Answer to Question 2
Participants must be volunteers. The study must be explained to them in detail. Care must be taken so that subjects are not harmed in any way. Subjects are free to cease participation in the study at any time. They have the right to confidentiality and/or anonymity, which means that their particular data cannot be connected to their name and/or that only the researcher knows their identity. Subjects should be debriefed after the study and have an opportunity to have any questions answered. If deception was used at the beginning of the study to protect the authenticity of the results or findings, then this should be clarified in the debriefing. Children and others who cannot give consent may have another responsible adult give consent on their behalf.
Obtaining consent from the elderly takes special care and must consider the person's ability to understand the study requirements. Human Subjects Review Boards evaluate all research studies to make sure participants are treated fairly and ethically. Any changes to the study protocol must be reevaluated by the review board.