The main functions of a market research company are the survey design, its production, conducting the fieldwork and the analysis.
The design is usually done by the management, research executives and assistants, whose task is to conceive and coordinate the study and make the report.
The production is carried out both by those people in charge of the quantitative, qualitative and telephone fieldwork (they manage the samples and the teams of interviewers).
The fieldwork itself is done by interviewers, most of whom are independent. Some companies do their own recruiting.
Other departments handle the coding, verbatim writing, data capture, tabulation and the all-important data processing. The IT department is very much involved with running the tables and carrying out multivariate analyses.