False negative what does it mean and why is it important?

shaun Big Data Enthusiast and lover of all things distributed and scalable.

False Negative

Also known as a type 2 error, a false negative means that you test negative and you actually have a disease.  This is important with a disease that spreads rapidly because of the chances that you could proceed with false confidence and continue to infect friends and loved ones.

For example

Suppose a disease infects 5% of society, and the test has a false negative rate of 20%.  For the sake of simplicity we will assume the disease does not produce false positives.   If you test negative for the disease what are the chances you have the disease, and should you worry?

Consider the matrix below of 1000 random people that have been tested.

  • 5% infection = 50 people actually have the disease
  • 20% false negative = 10 of those 50 test negative

What are the chances

10/950 = .0105 = 1% Chance

shaun

Big Data Enthusiast and lover of all things distributed and scalable.