推 nana0130:喔~~感謝感謝你>"< 11/01 13:40
→ a016258:我覺得你Z值跟查表的觀念要加強XD" 11/01 13:54
推 nana0130:感謝你~~我會低 11/01 15:52
※ 引述《nana0130 (小那)》之銘言：
: 1. 請問c 是多少?
: P(c <= |Z| )= 0.016
: 為什麼答案是 2.41
: 這不是說 c<= -Z and c<=Z 就代表c<=Z ??
: 我想不出來怎麼會是2.41
: 查表 Z值2.41是0.9920
=> P(c <= |Z| ) = P ( Z < -c ) + P ( Z > c )
= 2 P( Z>c ) = 0.016
=> P ( Z > c ) = 0.008
=> P ( Z <= c ) = 0.992
=> c = 2.41
: 2.Suppose the force acting on a column that helps to support a building
: is normally distributed with mean 15.0 kips and standard deviation 1.25
: kips.
: What is the probability that the force:
: b. Is between 10 and 12 kips? ans:0.0082
: 這題是不是 說P (12-15/1.25 <= Z <= 10-15/1.25)
: 12-15 /12.5 = -2.4 查表得 0.207
: 可是 10-15/1.25 = -4 Z表裡面查不到-4勒@@?
: 請問我哪裡錯了???
X is normally distributed with mean 15 , S.D 1.25
P ( 10 <= X <= 12 )
= P ( -4 <= (X-15)/1.25 <= -2.4 )
= P ( -4 <= Z <= -2.4 ) Z is standard normal
= 0.0082
P( Z<= -2.4 ) = P( Z>= 2.4 ) = 1 - P( Z<= 2.4) = 1 - 0.9918 = 0.0082 .
P ( Z<= -4) = 0
: c.differ from 15.0 kips by at most 1.5 standard deviations?
: 這什麼意思，是說把 standard deviations改成1.5 重算一次嗎 ?
: 謝謝
P ( |X-15| <= 1.5 * S.D )
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※ 編輯: a016258 來自: 114.42.198.17 (11/01 13:34)
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