Write a research problem that would be best studied using a probability sample.

A research problem could be of any topic. For example, you could make a research study based on the social status of people in the capital region. This would make a correlation with the country's economic performance. So, you gather around 1,000 respondents and you ask them some social class-determining questions. From your finding, you find that 823 of them belong to the lower class. Thus, the probability that a person in the capital region belongs to the lower class is equal to 823/1000 or 0.823.