Answer:
One area of marketing which is really relevant to a business success is the "market research" one.
One key of a business success is offering a product/service that your potential target market is looking for. You will find out by carrying out a precise market research.
Quantitative market research (surveys) is an essential stage in the business start-up process but many entrepreneurs don't do it - not least because of the supposed cost. Primary research determines the feasibility of a project and is a way to adapt a business' strategy (communication, pricing policy, products range…)