## Probabilistic Factors Involved in Disease and Virus Testing

Introduction This Insight looks at the various probabilistic factors and related terminology involved in disease and virus testing. As we all know, tests are rarely 100% reliable.  The frequency of false positives and false negatives, however, not only depend on the tests themselves, but also on the prevalence of the disease or virus within the…

## How to Solve Second-Order Partial Derivatives

Introduction A frequent concern among students is how to carry out higher order partial derivatives where a change of variables and the chain rule are involved.  There is often uncertainty about exactly what the “rules” are.  This tutorial aims to clarify how the higher-order partial derivatives are formed in this case. Note that in general…

## A Beginner Physics Guide to Baryon Particles

Introduction At the beginning of the 20th century, it was thought that all matter consisted of only three particles: the electron, the neutron, and the proton.  The major outstanding question was how the neutrons held the positively charged protons together within the atomic nucleus. In the search to answer that question, however, it was found…

## Demystifying the Chain Rule in Calculus

Introduction There are a  number of posts on PF involving a general confusion over the multi-variable chain rule.  The problem is often caused by a lack of clarity about the roles of functions and variables and what precisely each derivative means.  This insight is an attempt to clarify things. Part A: The Single-Variable Chain Rule…