Data can often be collected in different ways. Sometime it's through a census. Or it can be health information collected in the medical setting. Or it can just be a sampling of a larger population.
Before searching for your data, you may want to consider the format that you are looking for:
Based on what your need is, you may need different types of data. These sources will deal mostly with summaries, reports and a few opportunities to access full data sets.
Finding a source of statistics is only half the battle! You may want to consider some questions regarding bias: who collected the data? Are there any limitations to collecting this particular data? Remember, multiple sources can report on the same health issue but have different numbers. Consider your sources before citing!
For basic information about the people who live in Los Angeles
For health-related information in Los Angeles county and city