Three independent sensor measurements (mean ± standard deviation) are 4.52±0.02 V, 4.21±0.20 V and 3.96±0.15 V. Find uncertainty of their sum in V to two decimals.
Independence makes variances additive, rather than standard deviations. The sum’s standard uncertainty is √(.02²+.20²+.15²)=√.0629=.250799 V. Rounded to two decimals it is .25 V. The means sum to 12.69 V but do not enter this uncertainty calculation.
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