MATLAB: Neural network work better with small dataset than largest one

Deep Learning Toolboxneural network

Hi,i create neural network using nprtool at the begining i used input matrix with 9*981 but i got accuracy in the confusion matrix of 65% then i reduced the samples and i used input matrix with 9*102 and i got accuracy of 94.1% . So is this possible and correct ? and i want to know what's the reason for that.
Thanks

Best Answer

If the Input parameter in historical dataset(9*102) is highly correlated(important) with the target, it is possible. And I think historical dataset(9*981) is increased, but it seems to be decreases in correlation or Importance to the target.