data mining

Focus on deciding whether the results of two different data mining algorithms provides significantly different information.  Therefore, answer the following questions:

When using different data algorithms, why is it fundamentally important to understand why they are being used?
If there are significant differences in the data output, how can this happen and why is it important to note the differences?
Who should determine which algorithm is “right” and the one to keep?  Why?

Need in minimum 250 words