Left, Right

I used to think that I was good with numbers - a leftbrained person (for the record, I just had to look up on Wikipedia which qualities are left brained and which are right, even though I just asked someone about this a few days ago, which only goes to further the point, I suppose).  

Not that I was every particularly bad at rightbrained stuff like art and music.  I just always thought of myself as a math and science kind of guy.

Then I got to college and started scoring lower on tests.  Math tests, chemistry tests, physics tests - I just kept getting things wrong.  I became used to red ink all over my work.  By the end of college I decided that I was, in fact, rightbrained.  That would explain why I was so bad with numbers no matter how hard I tried.

Now, as I take these MCAT preparatory tests, I'm still making those math mistakes, but I'm evaluating them more closely.  More often than making fundamental mistakes in my analytical approach to solving a numbers question, I tend to just make plain old careless mistakes.  I missed a decimal point.  I left out a constant, or a minus sign.  That kind of thing.

Can a person be strong in his leftbrainedness but still make careless errors?  Or is it part and parcel of being leftbrained to not make those errors.

More importantly, maybe I should go into engineering after all.