Child my score higher simply because she was able to concentrate on the test and complain with the directions. There could be an equally smart child who just couldn't care less at that age and simple did what she wanted and therefore didn't answer some of the question even though she knew the answers. This is much more of an issue among 3 year olds than let's say 6 year olds.
The testing sample at that age had its own share of kids who didn't answer all the questions they could have because they didn't pay enough attention to the test. The norms are based on the sample so it may say that an average kid can answer 15 questions from such and such subtest when in reality an average kid is capable of much more if only she paid enough attention.
This will bring down the norms across the entire range. If your child scores in let's say 99% at the age of 3 chances are that there a few other kids who have the same knowledge/abilities but tested lower because they weren't interested enough in the test.
Of course, chances are pretty good that your daughter too didn't answer some of the questions for the very same reason.
I hope that makes sense.
