I am writing a research proposal and proposes to run a simple linear regression on impact of participation (independent variable) in social policy on well-being (dependent variable) of older people.
One suggestion that I have is for you to investigate the theoretical underpinning of the instrumentation you used to measure participation. For example, if I were using Talo and Mannarini's political and civic participation scale (Social Indicators Research, 123, 799-816), then I would look for my theory in their literature review discussing the development of their instrument.
Actually you can use the "ٍExpectancy Theory" involving the variables as "Satisfactions", "Rewards" and the relevant "Efforts", while applying the "Behavioral Management" as the mediating variable to mediate respective function in making well-being.