As a communications measurement consultant, I always hear:
Here are answers to the top three questions about survey samples:
1. How large does my sample need to be?
In survey research, a “sample” is a portion or subset of a larger group called a population. A population is the “universe” to be sampled. As most researchers know, a good sample is one that is representative of the population and exhibits similar characteristics—basically a miniature version of the population.
Conducting research with a sample is quick, efficient and much less expensive than with a total population (i.e., every employee in your company). Of course, if you have the capability and the budget, it is always best to do a “census” and survey everyone in the population.
This method allows everyone to have an opportunity to respond to the survey. In today’s real research world, however, most surveys are distributed to a “random sample.” This means that every “nth” person in the population is surveyed. The “n” is determined by the total population and how big you want your sample size to be. For example, if you had a total population of 1,000 and wanted 100 people in your sample, you would randomly select every 10th person to receive a survey.