Because of the nature of number generating algorithms, so long as the original seed is ignored, the rest of the values that the algorithm generates will follow probability distribution in a pseudorandom manner.
The choice of a good random seed is crucial in the field of computer security.
High entropy is important for selecting good random seed data.
Charting the output values of a PRNG with a scatter plot is a good way to find out if the seed is working.
If the graph shows static, then the PRNG is giving random results, but if a pattern appears, the seed needs to be fixed.