Final answer:
The availability heuristic is the cognitive bias that managers use to assess the frequency of an event by how easily they can recall similar instances, which may lead to distortions in perceived frequency or risk.
Step-by-step explanation:
The heuristic used by managers to assess the frequency of an event based on its ease of recall in memory is the availability heuristic. This cognitive bias occurs when individuals judge the likelihood of an event by how easily they can recall similar instances. When information about a certain type of event is more memorable or dramatic, people tend to believe that such events happen more frequently. The availability heuristic has significant effects on decision-making processes, especially in business and management, as it can lead to a skewed perception of risks and occurrences based on the most recent or notable examples rather than on statistical reality.