Final answer:
A survey would be the most useful tool for multi-national or single-country market research, as it can gather quantitative data about attitudes, beliefs, or habits of targeted populations.
Step-by-step explanation:
A survey would be most useful for multi-national or single-country market research. A survey is a structured interview that involves asking respondents the same set of questions to discover their attitudes, beliefs, or habits. The usage of surveys offers the ability to reach a large audience and can be modified to suit either large-scale studies like the U.S. Census or more targeted market research for specific populations such as customers of an electronics chain or library users.
For example, a marketing manager wanting to know customer ages might use a questionnaire given to a random sample of 100 customers at each store. A librarian could tally book checkouts to learn the proportion of children users. These methods ensure a representative sample that reflects the larger population. Ultimately, a well-conducted survey can provide vast amounts of quantitative data that are statistically analyzable, making it crucial for market research.