IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: donhassan on January 04, 2011, 07:57:52 pm

Title: statistics 1 question (cie)
Post by: donhassan 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
Title: Re: statistics 1 question (cie)
Post by: The Golden Girl =D on January 04, 2011, 08:05:10 pm: It would be better if you upload ,that way more members can help you
Title: Re: statistics 1 question (cie)
Post by: donhassan on January 04, 2011, 08:13:14 pm: Quote from: ~ The Golden Girl ~ on January 04, 2011, 08:05:10 pm
It would be better if you upload ,that way more members can help you
ok one min
Title: Re: statistics 1 question (cie)
Post by: The Golden Girl =D on January 05, 2011, 10:02:28 am: Okay.
Title: Re: statistics 1 question (cie)
Post by: Arthur Bon Zavi on January 05, 2011, 02:10:11 pm: I have a doubt there too.
Title: Re: statistics 1 question (cie)
Post by: Vin 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 / $\Sigma$ f 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.
Title: Re: statistics 1 question (cie)
Post by: Arthur Bon Zavi on January 13, 2011, 01:34:42 pm: Thanks man ! :D
Title: Re: statistics 1 question (cie)
Post by: donhassan on January 15, 2011, 04:50:33 pm: Quote from: Vin 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 / $\Sigma$ f 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