How do researchers decide on the size of a sample to use in quantitative research?

Question

Quizplus · Accepted Answer

The Answer is The decision about the best sample size depends on three things: 1)the degree of accuracy required,2)how variable or diverse the population is,and 3)the number of variables being simultaneously examined during data analysis.
Larger samples are required if one requires a high degree of accuracy,if the population is very mixed or contains lots of different elements (e.g.,lots of different ethnic groups in the case that ethnicity is a variable),and if the research is interested in examining many variables in the data analysis at the same time.
A smaller sample size is good enough when the population is similar (e.g.,in age,religious affiliation,etc.),and when only a few variables are examined at the same time during data analysis.

How Do Researchers Decide on the Size of a Sample