Final answer:
Personal background, interest groups, pollsters, and mass media are essential sources of public opinion, each contributing to the formation and reflection of societal views and beliefs.
Step-by-step explanation:
The sources of public opinion that are important include personal background, interest groups, pollsters, and mass media. Each of these plays a crucial role in shaping and reflecting public sentiment. Personal background affects opinions as individuals build beliefs based on their demographic characteristics like age, race, and gender. Interest groups influence public opinion by promoting their causes and trying to sway the public and policymakers. Pollsters measure public opinion through surveys and polls, although care must be taken to avoid biased samples. Mass media convey and sometimes shape public opinion by reporting news and providing forums for discussion.