If you are talking about the Revolutionary War, then the British were already an established independent government.
The correct answer is a representative portion of a universe in which each member of the universe has an equal chance of being included
A random sample is a subset of individuals (the sample) randomly selected from a larger set (the population) by a process that ensures that: All individuals in the population are equally likely to be chosen for the sample.
Responding to xenophobic concerns, Congress passed an emergency law restricting immigration in 1921. Among other provisions, the Act established a quota (a proportional share of a total) for nationalities on the basis of their numbers in the U.S. in 1910.
The missing detail is: a quota.