A collective noun is one that names more than 1 person, place, or thing. When the group is regarded as a unit, the singular verb is the appropriate choice. (See also 9.2, Plurals, Collective Nouns.)
The couple has a practice in rural Montana. [Couple is considered a unit here and so takes the singular verb.]
Twenty percent of her time is spent on administration. [Twenty percent is thought of as a unit, not as 20 individual units, and so takes the singular verb.] (See also 18.3.3, Units of Measure, Format, Style, and Punctuation, Subject-Verb Agreement.)
The paramedic crew responds to these emergency calls. [Crew is thought of as a unit here and so takes the singular verb.]
When the individual members of the pair or group are emphasized, rather than the group as a whole, the plural verb is correct.
The couple are both family physicians. [Couple is thought of as the 2 individuals who compose the couple, not as a unit, and so takes the plural verb.]
Ten percent of the staff work flexible hours. [Ten percent is thought of as being composed of each individual staff member, not as a unit, and so takes the plural verb.]
The surgical faculty were from all over the country. [Faculty here refers to the individual members of the faculty, rather than to the faculty as a group, and so takes the plural verb.]
The use of a phrase such as “the members of ” may make this last example less jarring.
The members of the surgical faculty were from all over the country.