any selection device has little meaning, but this is not often the case as there are usually more applicants than job openings. Finally, the base rate is defined by the percentage of employees thought to be performing their jobs satisfactorily following measurement. Selection decisions Tests designed to determine an individual's aptitude for a particular position, company or industry may be referred to as personnel assessment tools. Such tests can aid those charged with hiring personnel in both selecting individuals for hire and in placing new hires in the appropriate positions. They vary in the measurements they use and level of standardization they employ, though all are subject to error. Predictors for selection always have less than perfect validity and scatter plots, as well as other forecasting methods such as judgmental bootstrapping, and index models can help us to refine a prediction model as well as identify any mistakes. The criterion cutoff is the point separating successful and unsuccessful performers according to a standard set by the hiring organization. True positives are applied those thought to succeed on the job as a result of having passed the selection test and who have, in fact, performed satisfactorily. True negatives describe those who were correctly rejected based on the measure because they would not be successful employees. False negatives occur when people are rejected as a result of selection test failure, but would have performed well on the job anyway. Finally, false positives are applied to individuals who are selected for having passed the selection measure, but do not make successful employees. These selection errors can be minimized by increasing the validity of the predictor test. Standards for determination of the cutoff score vary widely, but should be set to be consistent with the expectations of the relevant job. Adjusting the cutoff in either direction will automatically increase the error in the other. Thus, it is important to determine which type of error is more harmful on a case-by-case basis. Banding is another method for setting cutoff values. Some differences in test scores are ignored as applicants whose scores fall with in the same band (or, range) are selected not on the basis of individual scores, but of another factor spas to reduce adverse impact. The width of the band itself is a function of test reliability, the two being negatively correlated. Banding allows employers to ignore test scores altogether by using random