deviation di xi x standard deviation s Sidi

[偏差](deviation): di = xi - x [標準差](standard deviation): s = (Sidi 2 /n)1/2 但次數n不大時, 誤差較大, 修正為 s = [Sidi 2 /(n - 1)]1/2 (不準度uncertainty/相對於準確度accuracy) x = x s or x = x s/x (%) (例) L = L s = 21. 93 0. 16 mm = 21. 93 mm 0. 73% [平均標準差](standard deviation of the mean) 如果作 N 組 n 個測量, 有 N 個平均值, 總平均值之標準差(平均標準差 ) 但如 N = 1, 平均標準差為 s(x) = s/ n = {Sidi 2 /[n(n-1)]}1/2 x = x s(x)/x (% or ppm/part per million) (例) 如 N = 1, n = 16 L = L s(L) = 21. 93 0. 04 mm = 21. 93 mm 0. 18 % (例) 電子質量 me = 9. 1093897 x 10 -31 kg (uncertainty 0. 59 ppm) (例) 光速 c = 2. 99792548 x 108 m/s (exact by definition)(1983) [計算時通常只取三位 3. 00 x 108 m/s ] (1 -4)