Definitions for

**"sample survey"**a process for collecting data on a sample of observations which are selected from the population of interest using a probability-based sample design

a way of collecting information on a subset of the elements of the target population with the intention of using the information to determine summary characteristics about the population

Every four out of five years, the R&D expenditures survey is conducted as a sample survey where only 25 percent of institutions in the probability category and all institutions in the certainty category are surveyed (as opposed to a full population survey which is conducted every fifth year and all institutions in the certainty and probability categories are surveyed). Data for institutions not sampled during a sample survey year are estimated through imputation.