PASS

This procedure gives power or required sample size for comparing two diagnostic tests when the outcome is sensitivity (or specificity). In this design, the outcome of each of two diagnostic screening tests is compared to a gold standard.

Specifically, a set of n subjects is randomly divided into two groups. In each group, a portion of the subjects have the disease (condition of interest) and a portion does not. Each subject is given the one of the diagnostic tests. Subsequently, a gold standard test is used to obtain the true presence or absence of the disease. The gold standard may be a more expensive test, difficult to determine, or require the sacrifice of the subject.

The measures of diagnostic accuracy are sensitivity and specificity. Sensitivity (Se) is the probability that the diagnostic test is positive for the disease, given that the subject actually has the disease. Specificity (Sp) is the probability that the diagnostic test is negative, given that the subject does not have the disease.

Li and Fine (2004) present sample size methodology for testing sensitivity and specificity using a two-group, prospective design. Their methodology is used in this procedure.

Minimum System Requirements
Click on one of the links below to view the minimum system requirements for NCSS and PASS products:
NCSS 8
PASS 11
PASS 2008
NCSS 2007
Previous Versions

Accuracy
We at NCSS have put a great deal of effort into finding the most accurate algorithms possible. The programs have been tested and verified over and over, both by us and by our customers. Each routine has been verified against textbooks, journal articles, and, where possible, other software. NCSS and PASS are some of the most accurate statistical analysis programs available. NCSS and PASS calculate with seventeen-digit, double-precision accuracy.

Guarantee
If you are not completely satisfied with an NCSS product during the first 30 days for any reason, return the program for a full, prompt refund (excluding shipping).