What are False Negatives and False Positives?
False Negatives are cases where an individual is diagnosed negative, but is in actuality positive. False negatives can be caused by the use of the wrong equipment (too little resolution to detect cysts which better equipment would have clearly shown), or because the sonographer was not skilled enough in using the equipment, or had not been trained sufficiently in the use and interpretation of ultrasounds, or had insufficient experience in diagnosing PKD by ultrasound. However, even with the best equipment and best sonographers, some false negatives will occur simply because of the inherent limitations of ultrasound. All ultrasound equipment has a limited resolution (higher wave-length transducers have better resolution than lower wave-length transducers), so any cyst that is smaller than the capabilities of the equipment to resolve cannot be differentiated from the surrounding kidney tissue. Even Dr. Biller himself reported 2% false negatives during his study (from cysts that were too
If an article is detected to contain reference to a company but really does not, we talk about a false positive. A source with the headline “Thai Air Safer Than Ever” could be detected as containing a reference to Thai Airways PLC. However, the article might really be about reduced pollution in Thailand. A false negative is the other way around: when an article actually does contain a reference to a company but it is not detected. Incompletely written company names will always increase risk of false negatives, although the RMI also does a good job here. • What if the article is in the grey zone area between positive and negative? In that case we will rather notify the user too many times than too few. Let’s say there was really 9 articles with a reference to TRUBB. Most users would rather receive 10 references with one not truly relevant than receive 8 relevant and missing one. Our data • How many sources do you acquire data from? Everything that might be relevant for Thai stocks. With
