This is the 2124th most frequent Japanese word.
平均
Average.
Here, "平均" (average) is used to indicate a typical or mean value in the context of family composition.
日本の平均的な家族構成は4人です。
The average Japanese family consists of four members.
"平均" in this context is utilized to denote the arithmetic mean, a statistical concept.
数学の授業で、平均値を計算する方法を学びました。
In mathematics class, I learned how to calculate the average value.
This usage of "平均" indicates an averaged measurement across a certain timeframe or activity.