grammatical number - Is "population" plural or singular?

For example, should I say:

The target population was selected ...

OR

The target population were selected ...

(please ignore passive voice issue)

Answer

In this example, 'target population' is functioning as the noun to the verb 'was'. What form of a noun - target population is a group, in my opinion [therefore a Mass or Collective noun]. When referred to as a group, a Collective noun will typically take a singular verb.

My Opinion- The target population was selected after the meeting with the Marketing team.

More on Subject-Verb agreement of Collective nouns:
Some subjects imply more than one person, but are themselves singular. These are known as collective nouns. Examples include group, team, committee, class, band, and family. Because these words are singular, they require a singular verb.

As the
subject of a sentence, a mass noun usually takes a singular verb {the litigation is varied}. But in a
collective sense, it may take either a singular or a plural verb form {the ruling majority is unlikely to
share power} {the majority are nonmembers}. A singular verb emphasizes the group; a plural verb
emphasizes the individual members.

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Edits: Almost all of the text. It is to accommodate the comments of @EFrog and @EdwinAshworth. A conclusive answer would depend on the certainty of the number of Collective noun. An ideal and unambiguous sentence should unequivocally substantiate that the noun be treated either as a group or as individuals of a group. Having said that, my answer/opinion stands on the ground of the sentence that I recommend in the answer. It is considered as Standard Written English under the ambit of cited sources. (I'll also consider applying for a job with Paralegal services hereafter;). Thanks for all your reviews/comments.

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