Data aggregation is any process in which information is gathered and expressed in a summary form, for purposes such as statistical analysis. A common aggregation purpose is to get more information about particular groups based on specific variables such as age, profession, or income. The information about such groups can then be used for Web site personalization to choose content and advertising likely to appeal to an individual belonging to one or more groups for which data has been collected. For example, a site that sells music CDs might advertise certain CDs based on the age of the user and the data aggregate for their age group. Online analytic processing (OLAP) is a simple type of data aggregation in which the marketer uses an online reporting mechanism to process the information. Answer: B is incorrect. Data aggregation can be user-based. Personal data aggregation services offer the user a single point for collection of their personal information from other Web sites. The customer uses a single master personal identification number (PIN) to give them access to their various accounts (such as those for financial institutions, airlines, book and music clubs, and so on). Performing this type of data aggregation is sometimes referred to as "screen scraping."