Bayesian statistics is a mathematical procedure that applies probability theory to statistical problems. It relies on conditional probability using the information to determine the likelihood of an event’s occurrence. Bayesian statistics update our beliefs when presented with evidence from new data and eliminates mistakes in our decisions. It uses A/B testing, which analyzes the performance of two groups to determine which is performing better and allows for leveraging multiple sources of data. Bayesian statistics relates a calculated quantity to one that can answer arbitrary questions-- used with a complex model with many measurement errors or multiple data sources. That is essential in marketing to determine which sales technique remains more effective. An example of this determines which internet page creates more sales of a product or service and permits effective webpage design to increase sales.