The Skills, Rules, Knowledge (SRK) framework or SRK taxonomy defines three types of behavior or psychological processes present in human performance.
Skill-based level: A skill-based behavior represents a type of behaviour that requires very little or no conscious control to perform or execute an action once an intention is formed. For example, bicycle riding is considered a skill-based behavior in which very little attention is required for control once the skill is acquired.
Rule-based level: A rule-based behavior is characterised by the use of rules and procedures to select a course of action in a familiar work situation. The rules can be a set of instructions acquired through experience or given by supervisors and former experience For example, hospitals have highly-proceduralized instructions for fire emergencies. Therefore, when one sees a fire, one can follow the necessary steps to ensure the safety of the patients without any knowledge of fire behavior.
Knowledge-based level: A knowledge-based behavior represents a more advanced level of reasoning. This type of control must be employed when the situation is novel and unexpected. Personnel are required to know the fundamental principles and laws by which the system is governed. Since personnel need to form explicit goals based on their current analysis of the system, cognitive workload is typically greater than when using skill- or rule-based behaviors. Engineering and design activities typically belong in this category.
You can see from the chart that the probability of making an error increases exponentially as you progress from skill, to rule, to knowledge based activities.