Statistical evaluations of diagnostic tests

In evaluating the clinical utility of any diagnostic test, including test instruments designed to select individuals for bone densitometry, several statistical measures are often used. The various measures are intended to indicate the probability of having or not having a particular disease based on the outcome of the test. Because bone density values are continuous data or variables, cut points must be selected that define the states of "diseased" and "nondiseased." Categories such as diseased and nondiseased are nominal data, as described earlier. Nominal data are necessary to determine probabilities. Cut points in bone densitometry are readily available by utilizing various T-scores or z-scores. The nominal data categories can then be described as at or above a certain standard score or, conversely, at or below a certain standard score. Once a cut point has been picked, a diagnostic test's utility in identifying diseased or nondiseased individuals can be characterized by its sensitivity, specificity, predictive value, and likelihood ratio. A receiver operating characteristic (ROC) curve can also be created to "test the test."

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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