Probability stratum

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NSF2: This survey is conducted through full population surveys every five years and sample surveys during the intervening four years. All institutions in the certainty stratum are surveyed every year. Only 25 percent of institutions in the probability stratum are surveyed during sample survey years. Institutions fall into the probability stratum when they do not qualify for the certainty stratum (i.e., the institutions are not doctorate-granting, selected university campus systems, historically black colleges or universities, or academically administered federally funded research and development centers). A complete description of the probability stratum category is available in the Methodology Report.