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Author Topic: S1 and S2 DOUBTS HERE!!!!  (Read 64662 times)

Offline Saladin

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S1 and S2 DOUBTS HERE!!!!
« on: May 04, 2010, 12:44:39 pm »
Hey, I do Edexcel S1, please post all your doubts here!!!
« Last Edit: July 30, 2011, 01:20:43 pm by ~Alpha »
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Offline Blizz_rb93

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Re: S1 DOUBTS HERE!!!!
« Reply #1 on: May 08, 2010, 06:47:30 pm »
Here's this question! I was solving through the book exercises and then I found this question a bit confusing.

A farmer keeps a record of the weekly milk yield of his herd of seven cows over a period of 6 months. He finds that the mean yield is 24 liters. He buys another cow that he is told will produce 28 liters of milk in a week. Work out the effect this will have on the mean milk yield of his cows.

Thank you in advance.
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Offline Summer :]

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Re: S1 DOUBTS HERE!!!!
« Reply #2 on: May 09, 2010, 05:15:31 pm »
i just face difficulties in answering those questions requiring comments :(
dunno what to do about it!! and those type of questions are more common nowdays then in the old papers  >:(
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Offline Saladin

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Re: S1 DOUBTS HERE!!!!
« Reply #3 on: May 09, 2010, 06:31:30 pm »
Quote from: Psyclax on May 08, 2010, 06:47:30 pm
Here's this question! I was solving through the book exercises and then I found this question a bit confusing.

A farmer keeps a record of the weekly milk yield of his herd of seven cows over a period of 6 months. He finds that the mean yield is 24 liters. He buys another cow that he is told will produce 28 liters of milk in a week. Work out the effect this will have on the mean milk yield of his cows.

Thank you in advance.


It will increase his yield to 24.5
\frac{24*7+28}{8}
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Offline Saladin

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Re: S1 DOUBTS HERE!!!!
« Reply #4 on: May 09, 2010, 06:32:46 pm »
Quote from: Summer :] on May 09, 2010, 05:15:31 pm
i just face difficulties in answering those questions requiring comments :(
dunno what to do about it!! and those type of questions are more common nowdays then in the old papers  >:(

It is best just to understand what the question is essentially asking. What is the question trying to investigate...

Sometimes, it just comes with practice.
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Offline Summer :]

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Re: S1 DOUBTS HERE!!!!
« Reply #5 on: May 10, 2010, 07:21:36 am »
Quote from: The Mysterious Dude on May 09, 2010, 06:32:46 pm
It is best just to understand what the question is essentially asking. What is the question trying to investigate...

Sometimes, it just comes with practice.
yeah true that..i prefer the C2 its more challenging  :)
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Offline T.Q

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Re: S1 DOUBTS HERE!!!!
« Reply #6 on: May 17, 2010, 12:18:02 pm »
help plz

Given that \mu=27  and \sigma^2= 10


find P(26 < X < 28).


my answer was  0.251

but in the MS the answer is 0.0796
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Offline Saladin

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Re: S1 DOUBTS HERE!!!!
« Reply #7 on: May 17, 2010, 05:27:46 pm »
Here is how you get it:

\frac{26-27}{\sqrt{10}}=-0.3162

\frac{28-27}{\sqrt{10}}=0.3162

Therefore,

The Probability is P(-0.3162<X<0.3162)

Therefore, P(X<0.32)= 0.6255

1-0.6255

0.3745*2

0.749

If I was using actual values, instead of statistical tables, I would have gotten your answer.


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Offline Saladin

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Re: S1 DOUBTS HERE!!!!
« Reply #8 on: May 17, 2010, 06:00:38 pm »
Quote from: T.Q on May 17, 2010, 12:18:02 pm
help plz

Given that \mu=27  and \sigma^2= 10


find P(26 < X < 28).


my answer was  0.251

but in the MS the answer is 0.0796

Which paper did you get this from?
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Offline immortal

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Re: S1 DOUBTS HERE!!!!
« Reply #9 on: May 17, 2010, 06:01:18 pm »
Quote from: T.Q on May 17, 2010, 12:18:02 pm
help plz

Given that \mu=27  and \sigma^2= 10


find P(26 < X < 28).


my answer was  0.251

but in the MS the answer is 0.0796
As per da MS dey hve taken S.D frm  \sigma^2= 10  as 10
but 10 is da variance, so da MS is wrong.While ur ans is correct.
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Offline T.Q

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Re: S1 DOUBTS HERE!!!!
« Reply #10 on: May 17, 2010, 06:10:42 pm »
Quote from: The Mysterious Dude on May 17, 2010, 06:00:38 pm
Which paper did you get this from?

jan 2004 q2
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Offline T.Q

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Re: S1 DOUBTS HERE!!!!
« Reply #11 on: May 17, 2010, 06:12:00 pm »
Quote from: immortal on May 17, 2010, 06:01:18 pm
As per da MS dey hve taken S.D frm  \sigma^2= 10  as 10
but 10 is da variance, so da MS is wrong.While ur ans is correct.


ya , i also think the MS is wrong
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Offline Saladin

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Re: S1 DOUBTS HERE!!!!
« Reply #12 on: May 17, 2010, 06:12:17 pm »
Quote from: T.Q on May 17, 2010, 06:10:42 pm
jan 2004 q2

Will check again, I dont think I am wrong though.

How did you get ur answer?
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Offline T.Q

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Re: S1 DOUBTS HERE!!!!
« Reply #13 on: May 17, 2010, 06:17:04 pm »
Quote from: The Mysterious Dude on May 17, 2010, 06:12:17 pm
Will check again, I dont think I am wrong though.

How did you get ur answer?

same as ur method

but at the end u have to subtract

1-0.749=0.251
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Offline T.Q

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Re: S1 DOUBTS HERE!!!!
« Reply #14 on: May 17, 2010, 06:21:20 pm »
Quote from: The Mysterious Dude on May 17, 2010, 06:12:17 pm
Will check again, I dont think I am wrong though.

How did you get ur answer?

paper link S1 jan 04
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