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在放射性测量中,在某个时间内对样品进行测量得到的计数值可以看成是一个随机变数。即使所有的测量条件都是稳定的,若多次记录在相同时间,内所测到的计数并不完全相同,而总是围绕着其平均值上下涨落。从理论上说,我们希望知道各个测量值所围绕着涨落的那个平均值,这个值应是无限次测量取值的平均值,即称为数学期望(真平均值)。而在实际测量中,我们只能进行有限次测量。一次测量值或有限次的平均值都不是真平均值。它们只能在某种程度上作真平均值的近似值,这样就给结果带来了误差,这是由放射性核衰变的统计性引起的,所以称为统计误差。
In a radiometric measurement, the count value of the sample measured at a certain time can be regarded as a random variable. Even if all measurement conditions are stable, if multiple counts are recorded at the same time, the counts are not exactly the same but always fluctuate around their averages. In theory, we want to know the average of the fluctuations around each measurement. This value should be the average of an infinite number of measurements, called the mathematical expectation (true average). In actual measurement, we can only make limited measurement. A measurement or a limited number of times the average is not a true average. They can only be approximated as true averages to some degree, thus giving rise to errors in results, which are caused by the statistical nature of radionuclide decay and are therefore called statistical errors.