人が一度に受け取ることのできる情報量

ユーザインターフェイスとか、プレゼンのパワポ作るとき、資料作成とかに役立つかもしれません。ぱっと見て情報が盛りだくさんだと一気に読む気が失せる、みたいな。

The rule of 7 ± 2 ( also known as Miller's Number ) derives from psychology research, which shows that the number of information "chunks" that a person can remember and manipulate at one time varies between five and nine. A larger number of chunks causes information overload. Information chunks can be many things, including names, words in a list, digits, or components of a picture.
Some applications of the rule of 7 ± 2 to DFDs (data flow diagrams) include the following.

A single DFD should have no more than 7 ± 2 processes.

No more than 7 ± 2 data flows should enter or leave a process, data store, or data element on a single DFD.

These rules are general guideline, not unbreakable laws. DFDs that violate these rules may still be readable, but violations should be considered a warning of potential problems.
Minimization of interfaces is directly related to the rule of 7 ± 2. An interface is a connection to some other part of a problem or description. As with information chunks, the number of connections that a person can remember and manipulate is limited, so the number of connections should be kept to a minimum. Processes on a DFD represent chunks of business or processing logic. They are related to other processes, entities, and data stores by data flows. A single process with a large number of interfaces ( data flows ) may be too complex to understand. This complexity may show up directly on a process decomposition as a violation of the rule of 7 ± 2. An analyst can usually correct the problem by dividing the process into two or more subprocesses, each of which should have fewer interfaces.

p215. Satzinger, Jackson, Burd. Systems Analysis & Design in a changing world. Thomson