S1 and S2 DOUBTS HERE!!!!

[Arthur Bon Zavi]

4. Questions 6b and c of January 2008 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20Jan/6683_01_que_20080115.pdf

(6) (b)

Weights between 190 and 210 are 60 %.

Now 60 % is equal to 0.6 of the probability right. So find out the value of si (0.6) which is equal to 0.7257 .

Now you know the formula :

                X - mean
Z =         -------------
          standard deviation

Let standard deviation be s.
So :

 210 - 200            190 - 200   
------------    -     ------------ = 0.7257
       s                         s

10 - (-10)
----------- = 0.7257
       s

20 = 0.7257s
s = 20/(0.7257)
standard deviation = 27.55959763 (or 27.56)


(c)

Use the same formula of normal distribution.
If you will use the original value of standard deviation (that is 27.55959763 and not 27.56), you will be benefited.

  180 - 200
---------------
27.55959763

= si (-0.7257)
= 1 - { si (0.726) }
= 1 - 0.766
= 0.234

So 0.234 is the probability that the customer will complain.

[Arthur Bon Zavi]

With explanation please, I have the marking scheme, so I know the answers, but I can't understand the working/how to do it! :/
Thanks alot!

Can you please provide all 4 marking schemes please ? Here itself.

[Arthur Bon Zavi]

What Master_Key told is correct. Sorry it just got deleted, while I was playing with my slow internet around.

Firstly, don't forget to add (+0.5) if you are finding probability of a greater than number like in your 3rd question it was more than 53 kg, otherwise you may get a penalty (loss of marks) - I don't know whether the same is practised in ED-EXCEL or not.

Lastly, if you don't want to forget to keep in (+0.5), just apply the formula without adding (+0.5):

1 - { si (<=X) }

[Alpha]

I'm sorry, your answers are wrong, check Fidato's post above for the right answer.

Apologies. I wasn't in my right state of mind. -.-

[**RoRo**]

Here they follow.

Done.

After 3 games Rohit has scored 6.
2 games are left and he has to get 4 points or more to win the prize.

List all the outcomes of the points he can get (see the image below).
You can see that there are 16 possible outcomes and six of which fetch him 4 points or more.
You know that :
P(0) = 0.4
P(1) = 0.3
P(2) = 0.2
P(3) = 0.1

So to win a price he should get points with the outcomes as follows (as circled in image).

{ (1,3) (2,2) (2,3) (3,1)(3,2) (3,3) }

Multiply and add the probabilities :

(0.3 X 0.1) + (0.2 X 0.2) + (0.2 X 0.1) + (0.1 X 0.3) + (0.1 X 0.2) + (0.1 X 0.1)

= 0.03 + 0.04 + 0.02 + 0.03 + 0.02 + 0.01
= 0.15

This one's right and I understood it, thank you!

I'm sorry, the link for the marking scheme for this paper is not opening now! :/

[**RoRo**]

(7) (c)

For this you need to find out the probability that the bag weighs more than 53 kg.


(a)

More than 53, so (53 + 0.5 = 53.5)

        53.5 - 50
Z =  ------------
             2
= si (1.75)
= 0.9599

Now, it's greater then 53, so :

   1 - { si (1.75) }
= 1 - 0.959
= 0.0401


(c)

2 bags greater than 53 kg and 1 less than 53 kg .

Probability that any bag is greater then 53 kg = 0.0401
and
Probability that it is less then 53 kg = 0.959

So :

³C₂ X (0.401)² X (0.959)
= 0.004630586
= 0.0046

The answer is wrong, the mark scheme is here: http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20June/S1%20june%2008%20ms.pdf

[**RoRo**]

(6) (b)

Weights between 190 and 210 are 60 %.

Now 60 % is equal to 0.6 of the probability right. So find out the value of si (0.6) which is equal to 0.7257 .

Now you know the formula :

                X - mean
Z =         -------------
          standard deviation

Let standard deviation be s.
So :

 210 - 200            190 - 200   
------------    -     ------------ = 0.7257
       s                         s

10 - (-10)
----------- = 0.7257
       s

20 = 0.7257s
s = 20/(0.7257)
standard deviation = 27.55959763 (or 27.56)


(c)

Use the same formula of normal distribution.
If you will use the original value of standard deviation (that is 27.55959763 and not 27.56), you will be benefited.

  180 - 200
---------------
27.55959763

= si (-0.7257)
= 1 - { si (0.726) }
= 1 - 0.766
= 0.234

So 0.234 is the probability that the customer will complain.

The answer is also wrong, the mark scheme is here:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20Jan/6683_01_rms_20080306.pdf

[**RoRo**]

Apologies. I wasn't in my right state of mind. -.-

No problem!

[Arthur Bon Zavi]

The answer is wrong, the mark scheme is here: http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20June/S1%20june%2008%20ms.pdf

In (a) there was a mistake so part (c) was influenced.

I took +0.5, so things happened.

You just find out the value of Z without adding (0.5) to 53, because at the end you have to subtract it from 1 anyhow.

I hope you understood and will do the (c) part yourself.

[Arthur Bon Zavi]

The answer is also wrong, the mark scheme is here:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20Jan/6683_01_rms_20080306.pdf

Oh ! I now realised that I had taken si (0.6) and not si^-1 (0.6).

Anyways I think you got that (+-) method that they have used. Actually P(X<210) = 0.8 so they have taken si^-1 ( 0.8 ) and nothing else.

[thecandydoll]

Hey
i just dont permutation and combinations.
any notes?
or what if i skip this question,I am fine with the rest of the question.
thanks

[EMO123]

Hey
i just dont permutation and combinations.
any notes?
or what if i skip this question,I am fine with the rest of the question.
thanks

but it is one of the scoring part of the paper
we just have to understand the condition of the question and do it

[Aadeez || Zafar]

Hey
i just dont permutation and combinations.
any notes?
or what if i skip this question,I am fine with the rest of the question.
thanks

see the video  of combination and permutation in KHAN ACADEMEY

would help u

i and my frnds had the sme problem but is solved now

[thecandydoll]

i tried...

[EMO123]

i tried...

try try and you will succeed