【正文】
Yuanyuan Tutor XuweiAbstract: In the classical probability model,the calculation of the sample points must be conducted in sample space what have been identified .How select the appropriate sample space of classical probability model .Even for the same problem. Only for the abstract description about sample space in the probability model .Due to the different research questions,Sample space is also different. It is difficult to understand the links and differences between the different sample space .When seeking the probability of something will lead to selection the wrong sample space and abuse sample space .The purpose of this paper is based on the correct ideas and theories about the underlying .By studying about typical example to analyze the general principles and best sample space. Construct the appropriate sample space by a symmetrical pression method to choose the best sample space and simplify the solution of classical probability model .Key words: classical probability model。 sample space。古典概型的求解包含兩個步驟:第一步:選取適當?shù)臉颖究臻g,使它滿足有限和等可能的要求, A是為的某個子集;第二步:先計算樣本點總數(shù)n,然后計算事件的有利場合數(shù)m。隨著科學技術的進步,概率論在科學中得到越來越廣泛的應用。1 古典概型變量古典概型也叫創(chuàng)痛概率,其定義是由法國數(shù)學家拉普拉斯提出的。眾所周知,最先吸引數(shù)學家研究的賭博問題就是分賭本問題:甲乙兩人賭技相同,各出賭資500元?,F(xiàn)在賭了三局,甲兩勝一負,因故要中止賭博,問這1000元要如何分才公平?有人認為按已勝的局數(shù)分,即甲拿三分之二,乙拿三分之一,但是這樣分是不合理的,因為設想繼續(xù)賭下去,結果無非以下四種:甲甲、甲乙、乙甲、乙乙。一個試驗是否為古典概型,在于這個試驗是否具有古典概型的兩個特征——有限性和等可能性,只有同時具備這兩個特點的概型才是古典概型。在第二部中要計算需要動用排列組合方法,但是排列組合具有技巧性和靈活性,給人難做的印象,下面則通過一些典型的例子具體討論重視第一步,即選擇適當?shù)臉颖究臻g的重要意義。 解 方法一:球依次被摸出,知道摸完為止,這就是把(a+b)個球全排列,所以這樣樣本點總數(shù)為(a+b)!,有利場合數(shù)為a(a+b1)!,所以p()=a(a+b1)!(a+b)!=a(a+b)。 第一個方法用排列組合的方法,方法二沒有。雖然方法一是最容易