depend on your application, work experience match with NOC, immigration points is very important too if you dont get or qualify minimum 67 points then application will reject too, IELTS result also play the role in certain NOC's, somany reason depends on each other , even if you dont fill your forms completely as per manual or missing documents not submit on time etc are also reason for rejection, before/after during review of your application by CIO / CHC.
OMM