Confidence Levels

A Disciplined Approach to Setting Probabilities

Photo by Edge2Edge Media on Unsplash

This article is one of a series of articles introduced by Flawed Reasons to Believe in God. If you’re new to the series, you should read the Introduction before (or after) reading the material below.

We live in a probabilistic world. Even simple activities like planning a weekend picnic depend on the odds of bad weather, the likelihood that chores won’t take up the whole weekend, and the probability that those chores can wait until a rainy day.

Unless you're a mathematician, you probably do not set numeric probabilities for each facet of a picnic, but the hidden calculator in your brain does it for you. Half cheese and half PB&J is close enough when calculating what kind of sandwiches to make. 52.7856% PB&J wouldn’t be a practical number to prepare. Anyone familiar with picnic planning knows that and plans accordingly.

Bayesian and Frequentist statistical analysis methods are more formal approaches to forming statistical inferences and being able to show the underlying work to others. The Frequentist method considers all available evidence and calculates a probability based on what’s known. A wise Bayesian begins with the Frequentist approach to set their prior, then adjusts the prior up or down as new evidence is discovered. Probabilities never reach 0% or…