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. 2013 Jul 3;8(7):e67284. doi: 10.1371/journal.pone.0067284

Table 1. Power frequency electric field measurements (V/m).

School N M±IR Min P25 P50 P75 Max Reference limit#
School A 30 0.417±0.84 0.016 0.108 0.417 0.949 2.919 4000 V/m
School B 21 1.34±2.83** 0.522 0.627 1.340 3.46 3.930 4000 V/m
#

Reference limit came from the Technical Regulations on Environmental Impact Assessment of Electromagnetic Radiation Produced by 500 kV Ultrahigh Voltage Transmission and Transfer Power Engineering (HJ/T24-1998) in China.

**

Two-Independent Samples Nonparametric Test, Z = 3.981, p<0.001.

N = number of spot measurements; M = median = P50; IR = interquartile range = P75–P25.