Final answer:
Marketing research, employee brainstorming, and creative methods such as advertising agencies all contribute to idea generation, the first stage of the product development process. Teams gather diverse ideas which are then narrowed down using a structured decision-making process to select the best concept.
Step-by-step explanation:
Marketing research, employee brainstorming, and outside sources such as advertising agencies are all potential sources of idea generation, which is the first stage in the product development process. In this stage, a variety of concepts are explored without much detail. Sources such as existing products, expert opinions, technical research, and customer feedback are gathered to generate potential designs. Teams use creative methods like brainstorming sessions, mind searches, and idea dumps to create a broad range of possible solutions. After generating a wide array of ideas, the design team typically uses a structured decision-making process to choose the best concept that fits the given criteria and constraints, which then moves forward to subsequent stages like concept development and testing.