Biostatistics
Biostatistics is the application of statistics to a wide range of topics in biology. It encompasses the design of biological experiments, especially in medicine, pharmacy, agriculture and fishery; the collection, summarization, and analysis of data from those experiments; and the interpretation of, and inference from, the results. A major branch is medical biostatistics, which is exclusively concerned with medicine and health.
Epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where) and determinants of health and disease conditions in defined populations.