Is the volume of data good enough?

While data mining, one mines the complete available data. But sometimes one can get a feeling that the data available is not complete. Is the data available good enough to reach to a conclusion with desired confidence and accuracy? Volume of data required depends on desired confidence level, desired accuracy and the variations in the data. Following article can be used in determining the volume of data needed.

http://edis.ifas.ufl.edu/PD006

Data Mining- Association rules

Though the following page is under construction but still this provides a good feel about what data mining is. It doesn't require much knowledge of mathematics. It gives idea about computation load and also can help in understanding the difference between data analysis and data mining.

http://www.iiit.ac.in/~vikram/mining.html