I don't know, sorry ...
When I was very little I rarely made mistakes but I was so slow it was rediculous.
When I got older I had to learn to hurry up and then I made a lot more mistakes.
I am a bit dyslexic so that made it worse too.
If you have time to check your answers try and check them a different way to how you did it in the first place.
If you go over the same working as before you are likely to overlook the same mistake....
ALWAYS check your answers if it is easy and/or if you have time.
ALWAYS look at your answer and consider if it is reasonable. eg if you get a probability of 1.5 then you should know it is wrong and you should state that even if you do not have time to redo it.
Sorry, I really do not have anything useful to say.....