i) In an open exanination, the average for a subject is 75, with a
standard of deviation of 8, the grades distribution follows a
normal distribution pattern. Determine the minimun mark for
Grade A for this subject if 15% of the students are given A's
ii) Three fair coins are tossed in an experiment
a) Find the probability of getting at least one head
b) Find the probability of getting exactly two head
Standard Distribution
2009-03-26 10:07 pm
回答 (2)
2009-03-26 10:52 pm
✔ 最佳答案
i. Let X be the mark got in the examination.Let C be the minimum mark required to get an A.
X ~ N(75, 82)
P(get A) = 15%
P(z > (C - 75)/8) = 0.15
(C - 75)/8 = 1.036521739
C = 83.3 (1 d.p.)
The minimum mark required is 83.3.
ii.a. P(at least one head)
= 1 - P(no head)
= 1 - P(3 tails)
= 1 - (1/2)3
= 7/8
b. P(exactly two heads)
= P(two heads and one tail)
= 3C2 X (1/2)2 X (1/2)
= 3/8
參考: Physics king
2009-03-27 12:10 am
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1998年度諾貝爾醫學得主LOUISIGNARRO 博土研發夜寧新。(MY BLOG有介紹)
有了一氧化氮(夜寧新)，可以遠離 高血壓、 糖尿病 、老年癡呆、性功能障礙 、中風、心臟病及強化心血管健康。
Herbalife美體纖柔霜及磨砂乳液改善肌膚粗糙和凹凸不平。
趕走〝熊貓眼〞及眼袋HerbalifeNouriFusion眼部啫喱。
暗瘡HERBALIFE日日滋養蘆薈潤膚啫喱！$HK107.0
MY BLOG：http://hk.myblog.yahoo.com/ChongMeiHung2
有健康營養、美容、身體護理、護髮
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