Final answer:
The outcome of having no fewer than 12 students living in the dorm is the least unusual situation given that 75% of a large university's students are expected to live in dormitories, which equates to about 15 out of 20 in a random sample.
Step-by-step explanation:
To determine which outcome of the random sample of 20 students is not unusual, we need to look at the expected number of students who live in the dormitories based on the given percentage. Since 75% of students live in the dormitories, we would expect 75% of the 20 students, which is 15 students, to live in the dorm. Therefore, having no fewer than 12 students live in the dorm is not unusual since it is close to the expected number.
Having fewer than 2 students who do not live in the dorm, which implies that 18 or more students do live in the dorm, isn't particularly unusual since it's slightly higher than what we expect, but still within a reasonable range considering it's a small sample size.
All 20 students living in the dorm or at most 10 students living in the dorm would be considered unusual occurrences, as these deviate significantly from the expected number of 15 students.