更新1:
If each of her serves is, independently of previous ones,. successful with probability 0.4, approximately what is the probability that she will need more than 100 serves to accomplish her goal?
Every day Jo practices her tennis serve by continually serving until she has had a total of 50 successful serves.?
回答 (1)
2016-02-08 8:49 pm
P(she will need more than 100 serves to have a total of 50 successful serves)
= P(she have a total of 0 successful serves in the first 100 serves)
+ P(she have a total of 1 successful serves in the first 100 serves)
+ P(she have a total of 2 successful serves in the first 100 serves)
+ ......
+ P(she have a total of 49 successful serves in the first 100 serves)
= 100C0 * 0.4º * 0.6¹ºº + 100C1 * 0.4 * 0.6^99 + 100C2 * 0.4² * 0.6^98 + ... + 100C49 * 0.4^49 * 0.6^51
= Σ (n = 0 to 49) 100Cn * 0.4ⁿ * 0.6¹ºº⁻ⁿ
= 0.9729...
= P(she have a total of 0 successful serves in the first 100 serves)
+ P(she have a total of 1 successful serves in the first 100 serves)
+ P(she have a total of 2 successful serves in the first 100 serves)
+ ......
+ P(she have a total of 49 successful serves in the first 100 serves)
= 100C0 * 0.4º * 0.6¹ºº + 100C1 * 0.4 * 0.6^99 + 100C2 * 0.4² * 0.6^98 + ... + 100C49 * 0.4^49 * 0.6^51
= Σ (n = 0 to 49) 100Cn * 0.4ⁿ * 0.6¹ºº⁻ⁿ
= 0.9729...
收錄日期: 2021-04-24 23:34:17
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https://hk.answers.yahoo.com/question/index?qid=20160205233440AAi9CNK