Ans: 20a) -2.5 b)11
21a)0.3675 b)$50.8 , $ 3.980
22) 94
pls show clear steps for the 3 questions.thanks!
更新1:
why the standard deviation in 21b) is 4 * 2 * √(0.55 * 0.45) ?? Is there a formula for this?
Special discrete prob. distrib
2011-09-20 4:23 am
http://i729.photobucket.com/albums/ww291/kaka1307/0497.jpg
Ans: 20a) -2.5 b)11
21a)0.3675 b)$50.8 , $ 3.980
22) 94
pls show clear steps for the 3 questions.thanks!
Ans: 20a) -2.5 b)11
21a)0.3675 b)$50.8 , $ 3.980
22) 94
pls show clear steps for the 3 questions.thanks!
回答 (1)
2011-09-20 5:45 am
✔ 最佳答案
20(a) Expected mark of each question when wild guesing= (1/4)(2) + (3/4)(-1)
= -0.25
So, the total expected mark is -2.5
(b) Total expected mark = 10[(0.7)(2) + (0.3)(-1)] = 11
21(a) C(4,2)(0.55)^2(0.45)^2 = 0.3675
(b) Expected value = 50 + 4(2 * 0.55 - 2 * 0.45) = 50.8
Standard deviation = 4 * 2 * √(0.55 * 0.45) = 3.98
22 (0.98)^n < 0.15
n > 93.9
So, the min. no. is 94
收錄日期: 2021-04-26 14:55:17
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110919000051KK00787