Recently I saw the results of an IQ test given with confidence intervals. While I know very well what a confidence interval is, I am not sure how you can give one for a psychological test. I think to determine a CI you either have to know the "true IQ" of an ensemble of persons and see how the results of the test scatter. Or you must be able to repeat the test with the same person and see how the results scatter on repetition. However, you neither know the true IQ nor can you repeat the same test with the same person as it will remember previous results.