Are the statistics relevant to your research?
Look at the type, depth and time range of data, and consider possible biases.
Are the statistics reliable?
Are they from an authoritative source such as the government or a recognised international organisation?
What methodology was used?
Many sources of statistics document the methodology used.
International statistics are dependent on the collection of data by national governments and other agencies, so the types, depth and dates of data are not always consistent between countries.
Collection of data within individual countries