Time intervals measured by a clock give the following readings 1.25 s, 1.24 s, 1.27 s, 1.21 sand 1.28 s. What is the  percentage relative error of the observations?        [NEET 2020]

Mean time interval, T¯=1.25+1.24+1.27+1.21+1.285=6.255=1.25 sMean absolute error, ΔT¯=ΔT1+ΔT2+ΔT3+ΔT4+ΔT55|1.25-1.25|+|1.24-1.25|+|1.27-1·25|⇒  =+|1.21-1.25|+|1.28-1.25|5⇒  =0+0.01+0.02+0.04+0.035=0.15=0.02 s∴ Percentage relative error =ΔT¯T×100=0.021.25×100=1.6%