어느 작업장에서 A물질의 농도를 측정 한 겨로가 각각 23.9ppm, 21.6ppm21.6ppm\mathrm{ppm}ppm21.6ppm, 22.4ppm22.4ppm\mathrm{ppm}ppm22.4ppm, 24.1ppm24.1ppm\mathrm{ppm}ppm24.1ppm, 22.7ppm22.7ppm\mathrm{ppm}ppm22.7ppm, 25.4ppm25.4ppm\mathrm{ppm}ppm25.4ppm을 얻었다. 측정 결과에서 중앙값(median)은 몇 ppmppm\mathrm{ppm}ppmppm인가?