Do all entering colleges students know what they want to major in, but me?

Of course not. It has been said that as many as 80% of entering students don't really know, even when they say that they are going to major in some field. Further, it has been found that undergraduates may give as many as four or five majors a test run by taking a trial course in that field. Still further, some students actually declare a major and then switch to something else later, often as many as two or three times before they graduate.