Final answer:
A useful survey must be administered to a representative sample from a larger population. The sample should match demographic distributions and include a random selection of individuals to ensure accurate representation and scientific validity.
Step-by-step explanation:
To be useful, a survey must be administered to a representative sample pulled from a larger population. Conducting a survey involves selecting a manageable number of subjects—the sample—that accurately reflects the larger population which is the focus of the study. For a sample to be considered representative, it should match the demographic distribution of the overall population, ensuring each member has an equal chance of being chosen (random sample). For example, in a representative survey, if the population is 51 percent female, then the sample should contain slightly more women than men to accurately reflect this. Furthermore, the sample size depends on the population being surveyed and the desired level of accuracy, with larger sample sizes often yielding more accurate results.
Pollsters and researchers apply various sampling methods to reduce bias and make sure their polls are scientifically valid. Random samples eliminate regional or other biases by giving every individual an equal chance of being selected, which is crucial for the survey's credibility. Opinion polls for presidential elections, for instance, typically include samples of 1,000-2,000 people to represent the entire country's viewpoint. To secure the effectiveness of the surveys, many pollsters employ statisticians and methodologists trained in the precise methodologies.