The average speed of a train is measured by 5 students. The results of measurements are given below

Mean value,vm=10.2+10.4+9.8+10.6+10.85=51.85=10.4  ms−1Δv1=vm−v1=10.4−10.2=0.2Δv2=vm−v2=10.4−10.4=0.0Δv3=vm−v3=10.4−9.8=0.6Δv4=vm−v4=10.4−10.6=−0.2Δv5=vm−v5=10.4−10.8=−0.4Mean absolute error,Δv¯=|Δv1|+|Δv2|+|Δv3|+|Δv4|+|Δv5|5=0.2+0.0+0.6+0.2+0.45=1.45=0.28  ms−1Relative error =±Δv¯vm=±0.2810.4Percentage error =±Δv¯vm×100=±0.2810.4×100=±2.6%