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混凝土试件强度标准差就相当于总体为正态分布的子样的标准差。本文对它的特性做简要介绍,同时用实测混凝土试件强度标准差加以佐证。说明试件组数越少,混凝土试件强度标准差的不定性越大,而且低于混凝土总体强度标准差的概率越高。所以用少量试件的强度标准差来估计混凝土总体强度标准差是不可靠的,而且大多偏小,对工程是不安全的,不能用来计算配制强度和验收强度。
The standard deviation of strength of concrete specimen is equivalent to the standard deviation of the subsamples with normal distribution. This paper gives a brief introduction of its characteristics, at the same time, it uses the measured standard strength of concrete specimens to prove. The results show that the smaller the number of specimens, the greater the uncertainty of the standard deviation of concrete specimens, and the higher the probability of less than the standard deviation of the overall strength of concrete. Therefore, the standard deviation of the strength of a small number of specimens to estimate the overall strength of concrete standard deviation is not reliable, and most of the small, the project is not safe, can not be used to calculate the strength of preparation and acceptance of strength.