When a market research is conducted then there are two sources of information which include internal and external sources. I think the internal sources of information give the most solid proofs as compare to the external sources of information. The internal sources of information include the people or the employees working in an organization, who is the part of the marketing research, newsletters of the companies, financial statements and management analysis reports etc. Just take an example for more clarification. If you are conducting a marketing research on, "impact of shelf positioning of FMCGs on impulse buying in a store". You can get the internal information from the sources including workers of the stores, distributors of a particular store, their databases etc.
