Step 1: Define supplier types in marketing research.
External suppliers broadly include:
(i) Syndicated-data providers — maintain continuous, standardized data (e.g., retail scanner panels, TV ratings) and sell the same dataset to many clients.
(ii) Custom research firms — design one-off studies tailored to a single client’s problem.
(iii) Specialty/fieldwork firms — focus on a sub-activity (sampling, interviewing, coding, analytics).
Step 2: Match options to definitions.
(a) “specialize in one or a few phases” describes specialty/fieldwork firms, not syndicated providers ⇒ reject.
(b) “studies for different client firms but in a different way” is vague and does not capture the shared, standardized nature of syndicated data ⇒ reject.
(c) “collect and sell common pools of data to several clients” = textbook definition of syndicated services (e.g., Nielsen, IQVIA, Kantar) ⇒ accept.
(d) “wide variety of customized services” describes custom research firms, not syndicated ⇒ reject.
Step 3: Why firms buy syndicated data.
Comparable metrics over time/markets, lower marginal cost per user, speed of access, and benchmarking across categories — all enabled by a standardized dataset.
Answer: (c)