Author Topic: statistics 1 question (cie)  (Read 1351 times)

Offline donhassan

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statistics 1 question (cie)
« on: January 04, 2011, 07:57:52 pm »
statistics 1 steve dobbs and jane millers is the book in it
pg 62 qustion 5
please solve it and explain how to do it

Offline The Golden Girl =D

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Re: statistics 1 question (cie)
« Reply #1 on: January 04, 2011, 08:05:10 pm »
It would be better if you upload ,that way more members can help you
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Offline donhassan

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Re: statistics 1 question (cie)
« Reply #2 on: January 04, 2011, 08:13:14 pm »
It would be better if you upload ,that way more members can help you
ok one min

Offline The Golden Girl =D

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Re: statistics 1 question (cie)
« Reply #3 on: January 05, 2011, 10:02:28 am »
Okay.
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Offline Arthur Bon Zavi

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Re: statistics 1 question (cie)
« Reply #4 on: January 05, 2011, 02:10:11 pm »
I have a doubt there too.

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Offline Vin

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Re: statistics 1 question (cie)
« Reply #5 on: January 12, 2011, 05:11:41 pm »
5. a, b easy.

a. standard deviation is 0. you need to understand the formula of SD on pg. 55 of the same book. you'll discover \Sigma x2f /\Sigmaf and \widetilde{x}, both equal 1, then only SD = 0.

b.

Ali => 12 * 1.07  =  12.84

Les => 16 * 0.76 =  12.16

Sam => 1 * 1   =  1

Therefore Ali is a clear winning, having caught highest mass of fish/

c.

Create a table for Sam's catch

Let 3rd fish caught be " a "

x     x f     x2 f

1      1        1
1       1       1
a        a       a2


\Sigma xf =  2+x

\Sigma x2 f = 2 + x2

\widetilde{x} = \frac{2+x}{3} <br />
 SD = 1

Using the SD formula and substituting the above values :

SD = \Sigma x2 f  /\Sigma xf - \widetilde{x}
root sign can be eliminate as SD = 1

1 = 2+x2/ 2+x -  (2+x/3)^ 2

simplify the eqn to get

2x2 -4x -7  = 0

solve this equation to get x= 3.12 and -1.12
omit the -ve ans so your ans =  3.12 kg

it ain't that complicated as it looks. i've tried my best to explain it well. go through the "theory" of variance and SD you'll figure.
« Last Edit: January 12, 2011, 05:16:00 pm by Vin »

Offline Arthur Bon Zavi

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Re: statistics 1 question (cie)
« Reply #6 on: January 13, 2011, 01:34:42 pm »
Thanks man ! :D

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Offline donhassan

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Re: statistics 1 question (cie)
« Reply #7 on: January 15, 2011, 04:50:33 pm »
5. a, b easy.

a. standard deviation is 0. you need to understand the formula of SD on pg. 55 of the same book. you'll discover \Sigma x2f /\Sigmaf and \widetilde{x}, both equal 1, then only SD = 0.

b.

Ali => 12 * 1.07  =  12.84

Les => 16 * 0.76 =  12.16

Sam => 1 * 1   =  1

Therefore Ali is a clear winning, having caught highest mass of fish/

c.

Create a table for Sam's catch

Let 3rd fish caught be " a "

x     x f     x2 f

1      1        1
1       1       1
a        a       a2


\Sigma xf =  2+x

\Sigma x2 f = 2 + x2

\widetilde{x} = \frac{2+x}{3} <br />
 SD = 1

Using the SD formula and substituting the above values :

SD = \Sigma x2 f  /\Sigma xf - \widetilde{x}
root sign can be eliminate as SD = 1

1 = 2+x2/ 2+x -  (2+x/3)^ 2

simplify the eqn to get

2x2 -4x -7  = 0

solve this equation to get x= 3.12 and -1.12
omit the -ve ans so your ans =  3.12 kg

it ain't that complicated as it looks. i've tried my best to explain it well. go through the "theory" of variance and SD you'll figure.
thanks dude