National sample is a research methodology that involves collecting data from a representative sample of individuals or households from across a country. This approach aims to provide insights into trends, attitudes, behaviors, and characteristics of the population as a whole. National sampling is typically used in large-scale surveys and studies to draw conclusions about the entire population and make informed decisions on policy matters, market research, and other areas. The sample is carefully selected to ensure that it is diverse and accurately reflects the demographics of the country.