我有啲懷疑老師唔識英文

As depicted by the above diagram, sample space is given by S, and there are two events A and B. In a situation where event B has already occurred, then our sample space S naturally gets reduced to B because now the chances of occurrence of an event will lie inside B.

As we have to figure out the chances of occurrence of event A, only a portion common to both A and B is enough to represent the probability of occurrence of A, when B has already occurred. The common portion of the events is depicted by the intersection of both the events A and B, i.e. A ∩ B.



計埋係啱的

前設joe係男呀

人哋係無錯，係你條柒頭理解錯

係呀，但係都要計
你係咪唔識睇英文

As depicted by the above diagram, sample space is given by S, and there are two events A and B. In a situation where event B has already occurred, then our sample space S naturally gets reduced to B because now the chances of occurrence of an event will lie inside B.
As we have to figure out the chances of occurrence of event A, only a portion common to both A and B is enough to represent the probability of occurrence of A, when B has already occurred. The common portion of the events is depicted by the intersection of both the events A and B, i.e. A ∩ B.

真，成班都小學學歷

provided that the first/second is male既話就係
但provided that one of them is male就唔係

如果 其中一個係男 同 另外一個係男 係independent event，
咁已知其中一個係男既機會係1-¼=¾, 兩個都係男既機會咪1.5/4 (但其實係¼)

又繼續,bb同gg點解唔洗分大細

感覺 1/2 係忽略咗個前設
無加到 Joe is a boy 呢個意思入去
純粹 設一個小朋友是男是女的 機會率

懶得搵, 再打過
個問題係究竟呀"Joe"係咪一個known person
即係佢只係一個隨機抽出黎的人定係已經固定左的人

前者等同於問"已知其中一個係男仔", 咁就會出到1/3:
P(2B | 1B) = P(2B ^ 1B)/P(1B) = P(2B)/P(1B) = (1/4)/(3/4) = 1/3
後者等同於問"有個仔女叫呀Joe, 已知係男仔, 咁就會出到1/2: 個問題等同於
given X_1, X_2 are independent random variables with P(X_i = 1) = P(X_i = 0) = 1/2, what is P(X_1 = X_2 = 1 | X_1 = 1)?

無錯啦，你條撚樣都識講第一舖，但topic問題無話joe係大仔，亦無要求joe係大仔

佢係計有機會發生既可能性，無機會發生既可能性係唔計

https://lih.kg/zoenDxX
#157 回覆 - 分享自 LIHKG 討論區

唔係 已經考慮咗 就係JB BJ JG GJ
而家個位係得出上面個4個option嘅probability(4/6)需唔需要考慮 題目已經前設咗oe係男 道理上呢4個option出現嘅probability=100%
但而家嘅解題機制係會consider埋4/6落去

兩個都係女唔係喺a或b

係我地計少左有JER既女人

LGBT+

整班冇讀過probability既人負評

https://mathseasy.hk/articles/conditional-probabilities/

當我們運用條件概率公式展開後，就要把已知的事件通通抹掉。即是在什麼都不知的前提下找其概率。

諗左好撚耐點解咁多負皮，決定歸咎係連登仔整體智商。

https://mathseasy.hk/articles/conditional-probabilities/

當我們運用條件概率公式展開後，就要把已知的事件通通抹掉。即是在什麼都不知的前提下找其概率。

用tree diagram 會唔會易理解啲？
因為唔係分大細，係分男女

1.joe 係大係仔，燃狗小菜係細係仔;

2.joe 係大係仔，燃狗小菜係細係女;

3.joe 係細係仔，燃狗小菜係大係仔;

4.joe 係細係仔，燃狗小菜係大係女;

5.joe 係大係女，燃狗小菜係細係女;

6.joe 係細係女，燃狗小菜係大係仔;

6個可能性，已知joe係仔，所以5同6可以直接排除

得返1-4 4個選擇，求兩個仔既機率，兩個仔出現情況係1同2 2個選擇，所以係2/4=1/2

啱

https://mathseasy.hk/articles/conditional-probabilities/

當我們運用條件概率公式展開後，就要把已知的事件通通抹掉。即是在什麼都不知的前提下找其概率。

GPT: The probability that Joe's sibling is a brother is 100%. If your neighbor has two children and you know one of them is a son named Joe, then it is certain that the other child is his sibling and also a brother.