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November 08, 2025, 08:15:34 am
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Author Topic: Normal distribution help!  (Read 3146 times)  Share 

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JV-12

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Normal distribution help!
« on: October 14, 2012, 08:27:47 pm »
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The weight of cats is normally distributed. It is known that 10% of cats weigh more than 1.8 kg and 15% of cats weigh less than 1.35 kg. Find the mean and the standard deviation of this distribution.

anyone have any ideas how to solve this question?
thanks!
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Jenny_2108

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Re: Normal distribution help!
« Reply #1 on: October 14, 2012, 08:31:20 pm »
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Quote from: JV-12 on October 14, 2012, 08:27:47 pm
The weight of cats is normally distributed. It is known that 10% of cats weigh more than 1.8 kg and 15% of cats weigh less than 1.35 kg. Find the mean and the standard deviation of this distribution.

anyone have any ideas how to solve this question?
thanks!

Pr(X<1.35)=0.15
Pr(X<1.8 )=0.9 

Solve these equations:





Edit: type wrong
« Last Edit: October 14, 2012, 08:46:18 pm by Ennjy »
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2012: Bio | Chem| Spesh | Methods | ESL | Vietnamese
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JV-12

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Re: Normal distribution help!
« Reply #2 on: October 14, 2012, 08:41:22 pm »
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would i solve the equations simultaneously?
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HERculina

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Re: Normal distribution help!
« Reply #3 on: October 14, 2012, 08:42:31 pm »
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Yep you would.
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JV-12

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Re: Normal distribution help!
« Reply #4 on: October 14, 2012, 08:49:57 pm »
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i'm still confused...my calculator came up with "no solutions"
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Jenny_2108

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Re: Normal distribution help!
« Reply #5 on: October 14, 2012, 08:54:20 pm »
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Quote from: JV-12 on October 14, 2012, 08:49:57 pm
i'm still confused...my calculator came up with "no solutions"





Solve simultaneous eq by hand or put in CAS, you get mean=1.55, sd=0.194
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Thanks to gossamer, TT, pi, laserblued, Thus for helping and supporting me during VCE

JV-12

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Re: Normal distribution help!
« Reply #6 on: October 14, 2012, 09:04:05 pm »
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thanks! i get it now :)
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