第三题我放弃(掩面) 以下答案仅供参考，错了不负责 中文题: (1) 即 1 - P(三个都不通电) = 1 - 0.4*0.2*0.1 = 0.992 //请拿小算盘验证一下 (2) 0.6*0.2*0.1 + 0.4*0.8*0.1 + 0.4*0.2*0.9 = 0.116 EX4. A random number is select from(0,π/2) what is the probability that is sine is greater than its cosine? -> 我这题没想出数学上的证明 只想到说画个sin和cos的图...答案很明显(?) EX5. Let x be a random variable. Assume that the distribution function F(x) = 0, if x<1 F(x) = (x^2-1)/8 , if 1≦x<3 F(x) = 1, if x≧3 1. Find and graph the density df(x)/dx = f(x) //即PDF的图 2. Find x such that probability -> 这题要倒过来做 先求出第二小题才能画第一小题的图 因为 PDF = CDF的微分 所以 f(x) = 0 , if x<1 f(x) = x/4 , if 1≦x<3 //我微分不行Orz 这边可以的话验算看看Q_Q f(x) = 0 , if x≧3 所以 ╱ ↑ ╱ 图大概长这样 注意一下相对应的值 │ ╱ 1/4│ 　╱ │ 　　　　　　　　　 │───────→　 1 3 EX2: A bag initially contains three black balls and two white balls 1. Alternatively, if the ball drawn from the bag is white then it's put back in the bag , other wise it's left out Draw a trellis diagram that illustrates the outcome space of this experiment 2. Find the probability of the sequence wwww and bbww for the experiment given in (ii) . Note that white and black are the balls drawn out first in the sequence wwww and bbww respectively ANS 1. 我觉得可能是我没看懂题目(?) 我画不出所有的样本 因为白球会丢回去... 大致上是这样: www........bbb www.......bwbb ....... 很多 = ="> www.......bwwb ANS 2. (a)wwww: 2/5 * 2/5 * 2/5 * 2/5 = 16/625 (b)bbww: 3/5 * 2/4 * 2/3 * 2/3 = 2/15 -- BED ▎●▅ ▅ ▎●▁▁ ▎●▅▅▅ ▎●▅▅ ┌ ▎ ┐ ▇▇▇ ▇ ▇▇▇▇ ▇▇▇▇ ●▅▅ ▇▇▇▇ │ ▇▇▇▇ │ & ▎ ▎ ▎ ▎ ▎ ▎ ▎●▅▅ │ ▎ ▎│ ▇▇▇▇ │ │ I magician super model basketball homeless prisoner └ engineer ┘ --

※ 发信站: 批踢踢实业坊(ptt.cc) ◆ From: 203.68.15.28 ※ 编辑: gingkoginkgo 来自: 203.68.15.28 (05/14 01:58) ※ 编辑: gingkoginkgo 来自: 203.68.15.28 (05/14 01:58)