This is a question that we are often asked. For instance:
Dear Educational Psychologist
We are interested in an assessment with you for our daughter she is 7 years old. We suspect she may have dyslexia. Is it still possible to detect with any certainty that she does/does not have dyslexia?
My reply:
Dear Mr and Mrs Another,
I can test underlying ability (IQ) and literacy skills then make a statistical comparison, this would lead to, two possible conclusions that there is or is not a statistically significant discrepancy between individual literacy scores e.g. word reading accuracy and underlying ability to a reasonable degree of scientific certainty. At this point if there is a discrepancy to a reasonable degree of scientific certainty, then the psychologist makes a judgment call based upon historical evidence of intervention to diagnose a specific learning difficulty, such as dyslexia. If there is no statistically significant discrepancy then the psychologist may reject the hypothesis of a specific learning difficulty or based upon the totality of the assessment identify anomalies in functioning and performance that whilst they are not statistically significant still cause concern, for instance the psychologist might observe an inconsistent pattern to reading for comprehension performance, and suggest intervention All of this assessment would be included in our fixed fee assessment.
http://www.educational-psychologist.co.uk/find-an-educational-psychologist/