As Jamie suggests Scott its a big and complicated subject with the actual Intelligence Quotient dependent on not just intelligence but also how it relates to age and on which type of test you use. Not everyone is good at puzzle solving but that doesn't mean that someone has a low IQ just because they get a low reading on a test that centres on such problems.
If it is of any help our youngest daughter is registered as having 'special needs' due to 'global developmental delay' which actually presents itself as 'autistic tendencies' although she is not actually autistic. Even so she struggles with reading, writing and arithmetic but with the right sort of help (she has a classroom assistant who can help her understand what is written on the board for example) she can really shine and is currently amongst the top set for science.
So she is no idiot, but if you gave her an IQ test.... well, I very much doubt she would get beyond adding her name.
By all means PM me if you want more details.