Final answer:
Perfect reliability in a reliability coefficient is represented by a value of +1 or -1, while complete unreliability is indicated by a value of 0. Thus, perfect reliability is a high value and complete unreliability is a low value.
Step-by-step explanation:
When evaluating a reliability coefficient, perfect reliability is represented by a coefficient value of +1 or -1, which would mean the variables are perfectly linearly related. Complete unreliability is represented by a coefficient value of 0, indicating no linear relationship. Thus, the correct response to what represents perfect reliability and complete unreliability is: 1) A high value, a low value. Values closer to +1 or -1 signify stronger relationships, whereas values near zero signify weaker or non-existent linear relationships.