Signal ditection.docx
- 1. EXPERIMENTAL PSYCHOLOGY SIGNAL DETECTION THEORY SUBMITED: BY ANDLEEB FAYYAZ TO MAM: RAUMISH MASUD KHAN DATE: 28/01/2014
- 2. SIGNAL DETECTION THEORY Definition “Signal detection theory deals with the delectability of signals and criterion that are used for the detection of signals” Explanation This theory can be an application of psychologysics because the observer’s response is according to their sensitivity to stimulus and the judgment is accordingly. Signal detection theory is basically a sensory experiment to us and it helps us to analyze much kind of decision making problems. Information and criterion For example a radiologist is looking for evidence of tumor. Interpreting images on CT scan is hard and need a lot of experience to interpret a tumor. There is always uncertainty about the presence of tumor or not. 4 possibilities of detection the stimulus Doctor sees the tumor and says “yes” Hit (tumor present and doctor says “yes”) Miss (tumor present and doctor says “no”) False alarm (tumor absent and doctor says “yes”)
- 3. Correct rejection (tumor absent and doctor says “no”) Present Hit False alarm Yes Miss No absent Correct rejection Decision making process Decision making process involves Information acquisition and Criterion Information acquisition Healthy lungs are of different shape and lungs a tumor may have a different image . Characteristics 1. Brighter or darker 2. Different texture When doctor get complete training he or she learn what kind of tumor they looking for.
- 4. With more training they will be able to acquire more information increased information increase the possibility of errors. Criterion 1. In addition to use technology to gain information a doctor also uses his own judgment. 2. Different types of errors are not equal for example missing the opportunity of earns diagnosis means that difference between life and death. A falls alarm is further tested through routine biopsy operation. They may choose the “yes” decision. 3. Other doctors may be more conservative and give the repute of “no” (no tumor) to reduce the unnecessary surgery. 4. The doctor may pick up the tumor at net check up. Internal response and internal noise There are two kinds of noise factors that produce uncertainty. 1. Internal noise 2. External noise External noise Many sources of external noise are there which can be the part of photographical process. Like a smudge or something in the person’s lung that is looks like a tumor. They are the example of external noise. Doctor can reduce the external noise but there is nothing to reduce the internal noise.
- 5. Internal noise Suppose that doctored has a set of tumor detector neurons and he determines the tumor as his neurons responds to the image (actually the doctor detect a thing which is looks like tumor) PURPOSE AND APPLICATIONS 1. It is applied to humans and as well as other animals. 2. Application in a recognition paradigm. 3. Sensitivity index: used in statistics for computing. 4. Non parametric measures: it means the area which comes under the ROC curve. Bias: bias is independent of the sensitivity (a person may be more likely to respond at the stimulus or more likely to respond at the stimulus which is not present. PURPOSE OF SIGNAL DECETION THEPRY 1. The purpose of signal detection theory is to increase the sensitivity of stimulus. 2. Various disciplines: I. Psychology II. Audiology III. Speech perception IV. Engineering V. VI. Animal psychology Medical forensic science weather forecasting. 3. Audition: the application which is applied in clinical measurement of threshold or stimulus.
- 6. 4. Speech perception: used in the recognition speech messages and to carried out psychophysics researches. 5. Psychology: in the field of memory and attention. 6. Engineering: it is also used in x-rays, in CAT scan for the interpretation of cancer or tumor. 7. Short increment sensitivity index: to test hyper sensitivity to small change in intancity and developed the SISI test.