Self-study
All of the students at Harrison University live in one of two residence complexes, either Pulham or Westerville. ████████ ████ █ █████ ████████ ██ ███ ███████ ██ ████████ ███ █████ ████████ ██ ███████ ██ ████████ ████████ ████ ██ █████ ███ █████ ██████ ████ ██████ ██ █████ ███ ████████ ████████ ██████ ██ ████████████ ████ ██ ███████ ██ █████ ████████ ████ ██ █████ ███ █████ ██████
Summary
All Harrison University Students live in either Pulham or Westerville.
A small fraction of the classes at Harrison are night classes.
38% of Harrison students take at least one night class.
29% of students living in Westerville take at least one night class.
Notable Valid Inferences
If a student doesn’t live in Westerville, the student lives in Pulham.
Over 38% of students living in Pulham take at least one night class.
21.
If the statements above are █████ █████ ███ ██ ███ █████████ ████ ████ ██ █████
a
More than 38 ███████ ██ ███ ████████ ██ ████████ ███ ████ ██ ██████ ████ █ █████ ██████
Must be true. Since all students live in either Pulham or Westerville, the overall 38% night-class enrollment is an average of both groups. Westerville students have a lower rate (29%), meaning Pulham students must have a higher rate to balance the overall percentage at 38%.
b
More than 50 ███████ ██ ███ ████████ ███ ████ █████ ███████ ██ ████████ ███ ████ ███████
Could be false. We don’t know how many students live in each dorm. It could be the case that Westerville has more students than Pulham––in this case, over 50% of the night class students would be from Westerville, even though only 29% of Westerville students take night classes.
c
More students at ████████ ████ ██ ███████████ ████ ████ ██ ███████
Could be false. We don’t know anything about the relative sizes of the two residence complexes.
d
Harrison students living ██ ██████ ███ ████ ██████ ████ █████ ██████ ██ ███████████ ██ ████ ████ ████ ███ █████ ██████
Could be false. We don’t know anything about people who take more than one night class. The stimulus only discusses students who take at least one night class.
e
Night classes at ████████ ████ ██████ ████████████ ██ ████████ ████ ███ ███████ ███
Could be false. We don’t know anything about the enrollment size of day classes.