To develop a model, a creditor selects a random sample of its customers, or a sample of similar customers if their sample is not large enough, and analyzes it statistically to identify characteristics that relate to creditworthiness. Then, each of these factors is assigned a weight based on how strong a predictor it is of who would be a good credit risk. Each creditor may use its own credit scoring model, different scoring models for different types of credit, or a generic model developed by a credit scoring company.
Under the Equal Credit Opportunity Act, a credit scoring system may not use certain characteristics like -- race, sex, marital status, national origin, or religion -- as factors. However, creditors are allowed to use age in properly designed scoring systems. But any scoring system that includes age must give equal treatment to elderly applicants.