From the Document: " The NHS [National Household Survey] assesses how the culture of personal disaster preparedness and resilience has changed over time in the United States.  FEMA has conducted this survey annually since 2013.  The NHS is a 'telephone interview survey' in which both landlines and cell phones are selected randomly to answer a set of survey questions.  FEMA selects a larger set of phone numbers in certain areas of the country that are at higher risk of one of 'six hazards', to gain more information from residents in those areas. These are called 'oversamples' (one oversample taken for each of these hazards).  In the '2019 NHS', FEMA interviewed '5,025 adults' (aged 18 years and older)."
Federal Emergency Management Agency: https://www.fema.gov/