从一副 52 张牌中得到 10 或 J 的概率是多少?
概率意味着可能性。它说明事件即将发生的可能性。事件的概率只能存在于 0 和 1 之间,其中 0 表示事件不会发生,即不可能,1 表示肯定会发生,即确定性。
事件发生的概率越高或越小,事件发生或不发生的可能性就越大。
例如 –一枚无偏的硬币被抛一次。因此,结果的总数只能是 2,即“正面”或“反面”。两种结果的概率相等,即 50% 或 1/2。
因此,事件的概率是有利结果/结果总数。它用括号表示,即P(Event)。
P(Event) = N(Favorable Outcomes) / N (Total Outcomes)
Note: If the probability of occurring of an event A is 1/3 then the probability of not occurring of event A is 1-P(A) i.e. 1 – (1/3) = 2/3
什么是样本空间?
事件的所有可能结果称为样本空间。
例子:
- A six faced dice is rolled once. So, total outcomes can be 6 and
Sample space will be [1, 2, 3, 4, 5, 6]
- An unbiased coin is tossed, So, total outcomes can be 2 and
Sample space will be [Head, Tail]
- If two dice are rolled together then total outcomes will be 36 and
Sample space will be
[ (1, 1) (1, 2) (1, 3) (1, 4) (1, 5) (1, 6)
(2, 1) (2, 2) (2, 3) (2, 4) (2, 5) (2, 6)
(3, 1) (3, 2) (3, 3) (3, 4) (3, 5) (3, 6)
(4, 1) (4, 2) (4, 3) (4, 4) (4, 5) (4, 6)
(5, 1) (5, 2) (5, 3) (5, 4) (5, 5) (5, 6)
(6, 1) (6, 2) (6, 3) (6, 4) (6, 5) (6, 6) ]
活动类型
独立事件:如果两个事件(A 和 B)是独立的,那么它们的概率将为 P(A 和 B) = P (A ∩ B) = P(A).P(B) 即 P(A) * P(B )
Example: If two coins are flipped, then the chance of both being tails is 1/2 * 1/2 = 1/4
互斥事件:
- 如果事件 A 和事件 B 不能同时发生,则称为互斥事件。
- 如果两个事件互斥,则两者发生的概率记为 P (A ∩ B)
和 P (A 和 B) = P (A ∩ B) = 0 - 如果两个事件互斥,则任一事件发生的概率记为 P (A ∪ B)
P (A 或 B) = P (A ∪ B)
= P (A) + P (B) - P (A ∩ B)
= P (A) + P (B) - 0
= P (A) + P (B)
Example – The chance of rolling a 2 or 3 on a six-faced die is P (2 or 3) = P (2) + P (3) = 1/6 + 1/6 = 1/3
不互斥事件:如果事件不互斥,则
P (A or B) = P (A ∪ B) = P (A) + P (B) − P (A and B)
什么是条件概率?
对于某个事件 A 的概率,给出了某个其他事件 B 的发生。写成 P (A ∣ B)
P (A ∣ B) = P (A ∩ B) / P (B)
示例-在一袋 3 个黑球和 2 个黄球(共 5 个球)中,拿一个黑球的概率是 3/5,拿第二个球的概率是黑球或黄球取决于先前取出的球。因为,如果拿了一个黑球,那么再次捡到一个黑球的概率是 1/4,因为只剩下 2 个黑球和 2 个黄球,如果之前拿过一个黄球,那么再次捡到一个黑球的概率是黑球将是 3/4。
与卡片相关的一些要点:
- 一副牌中有 52 张牌。
- 在 52 张牌中,每种颜色有 26 张牌,即 26 张红牌和 26 张黑牌。
- 在 26 张红牌中,有 2 套花色,每套 13 张牌,即 13 张红心牌和 13 张菱形牌。
- 在 26 张黑牌中,有 2 套花色,每套 13 张牌,即 13 黑桃和 13 张梅花牌。
- 每个套件有 13 张牌,从 2 到 10,J、Q、K 和 A,这意味着每种类型 4 张牌。
- J、Q 和 K 被称为面卡。
从一副 52 张牌中得到 10 或 J 的概率是多少?
回答:
Total number of cards are 52 and number of jack cards are 12 and number of 10 is 4.
So, total outcomes = 52
Favorable outcomes = 4 + 4 = 8 (4-10s and 4-Js)
So, the probability of getting a 10 or a Jack = Favorable outcomes / Total outcomes = 8 / 52 = 2/13
P(10 or J) = 2/13
类似问题
问题1:得到J或黑牌的概率是多少?
解决方案:
Total number of cards are 52 and number of black cards are 26 and jacks are 4 whereas 26 black cards contain 2 Jacks(so only 2 will be considered out of 4)
So, total outcomes = 52
favorable outcomes = 26 + 2 = 28
So, the probability of getting a jack or black card = Favorable outcomes / Total outcomes = 28 / 52 = 7/13
P(JorB) = 7/13
问题 2:得到一张皇后牌或方块牌的概率是多少?
解决方案:
Total number of cards are 52 and number of diamonds cards are 13 and queens are 4 whereas 13 diamond cards contain 1 Q(so only 3 will be considered out of 4)
So, total outcomes = 52
favorable outcomes = 13 + 3 = 16
So, the probability of getting a queen or a diamond card = Favorable outcomes / Total outcomes = 16/ 52 = 4/13
P(QorD) = 4/13
问题3:得到J或红牌的概率是多少?
解决方案:
Total number of cards are 52 and number of red cards are 26 and jacks are 4 whereas 26 red cards contain 2 Jacks(so only 2 will be considered out of 4).
So, total outcomes = 52
favorable outcomes = 26 + 2 = 28
So, the probability of getting a jack or red card = Favorable outcomes / Total outcomes = 28 / 52 = 7/13
P(JorR) = 7/13