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〔上接《宁夏医学杂志》1988;10(l):54〕欲知上例实际资料与普哇松的理论分布是否一致,需将表5的(A)、(T)两栏作x~2测验。经统计处理后,其x~2 值=0.1792。本例自由度(n′)为 3-2=1。查x~2值表,知机率(P)>0.05。即实际资料与普哇松分布无显著区别,亦即相当一致。 (3)注意事项:普哇松分布,机率(P)往往很小,但数值往往不甚明确;各组的频数(K)应该是大的,但必须限制在适当狭窄的范围内。一般认为液体中的细菌计数,放射性物质中α-、β-射线的放射,感光物质由于光电作用而放射电子等等,符合于普哇松分布。从理论上讲,平均数<10时即可做普哇松分布的概括,但习惯上认为平均数<5者普哇松分布的配合较好。 3.常(正)态分布(Normal distribu-tion):常态分布是对称的二项式分布(1/2+1/2)~K式中K值趋于无限大时得到的光滑曲线。这条曲线的特点是:形态为对称钟形,平均数在最高点;离开对称分布将是偏态,离开常态峰频数将过多或过少地集中在
[Ningxia Medical Journal 1988; 10(l):54] To know if the actual data of the above example is consistent with the theoretical distribution of PuHua Song, the two columns (A) and (T) of Table 5 shall be used as x 2 quiz. After statistical processing, its x~2 value = 0.1792. In this example, the degree of freedom (n’) is 3-2=1. Check the x~2 value table, and the probability (P)>0.05. That is, there is no significant difference between the actual data and Puhuasong distribution, which is quite consistent. (3) Note: Puhuasong distribution, the probability (P) is often very small, but the value is often not clear; the frequency (K) of each group should be large, but it must be limited within the appropriate narrow range. It is generally considered that bacteria count in liquids, radiation of α-, β-rays in radioactive substances, photoreceptor substances emit electrons due to photoelectric effect, etc., which are in accordance with Puhuasong distribution. Theoretically speaking, the average Puwson distribution can be summarized when the average number is less than 10, but it is customary to think that the Puwosong distribution is better with an average of <5. 3. Normal (normal) distribution: Normal distribution is the smooth curve obtained when the K value in the symmetric binomial distribution (1/2 + 1/2) ~ K is approaching infinity. The characteristic of this curve is that the shape is symmetrical and the average is at the highest point; leaving the symmetry distribution will be skewed, and leaving the normal peak frequency will be concentrated too much or too little.