Final answer:
Commercial sources can provide demographic, financial, and weather data, all of which are useful for different industries and purposes.
Step-by-step explanation:
The data that can be purchased from commercial sources includes demographic data, financial data, and weather data. Demographic data can be obtained through vital statistics registries and censuses, which provide information on variables such as age, sex, marital status, and more. Financial data often involves quantitative data obtained through in-depth analyses and can include information on markets, investments, and corporate finances. Weather data, collected through various meteorological methods, is also commercially available and includes daily forecasts, historical weather patterns, and climate statistics.