Facebook is testing technology that would greatly expand the scope of data that it collects about its users, the head of the company’s analytics group said Tuesday. The social network may start collecting data on minute user interactions with its content, such as how long a user’s cursor hovers over a certain part of its website, or whether a user’s newsfeed is visible at a given moment on the screen of his or her mobile phone, Facebook analytics chief Ken Rudin said Tuesday during an interview. Mr. Rudin said the captured information could be added to a data analytics warehouse that is available for use throughout the company for an endless range of purposes–from product development to more precise targeting of advertising. Facebook collects two kinds of data, demographic and behavioral.