This discussion is now closed.

Check out other Related discussions

The Edexcel S1 (18/05/12 - AM) Revision Thread

Hello
Do you have any tips on those wordy questions "suggest why..." I always am losing marks on those silly questions. My teacher said "if you see such questions simply waffle on and you might get the mark" but this is not helping me. Do you guys get them rights always and any tips too?

What marks are you getting
and how much revision have you all done?

thank you

Reply 381

Asyfa

3. When Rohit plays a game, the number of points he receives is given by the discrete
random variable X with the following probability distribution.
x 0 1 2 3
P(X = x) 0.4 0.3 0.2 0.1

Rohit can win a prize if the total number of points he has scored after 5 games is at least
10. After 3 games he has a total of 6 points.
You may assume that games are independent.
(e) Find the probability that Rohit wins the prize. (6mark)

can anyone help me on this ques?... its from jan 09 paper questionn 3 e

Reply 382

Gawjuz.x

Original post by Asyfa

3. When Rohit plays a game, the number of points he receives is given by the discrete
random variable X with the following probability distribution.
x 0 1 2 3
P(X = x) 0.4 0.3 0.2 0.1

Rohit can win a prize if the total number of points he has scored after 5 games is at least
10. After 3 games he has a total of 6 points.
You may assume that games are independent.
(e) Find the probability that Rohit wins the prize. (6mark)

can anyone help me on this ques?... its from jan 09 paper questionn 3 e

I had the same problem with this question as well. This is how to tackle it:

Rohit can win a prize after 5 games the total number of points is 10. He has played 3 games so far and has scored 6 points.

3 games 6 points

This means in the 2 remaining games he needs to get ≥ 4

Let’s look at the possibilities:

1 & 3 or 3 & 1
Working out the probabilities (looking at your tables this would be) 0.03 * 2 = 0.06 (the reason that we multiply by 2 is there are two different permutations)

2 & 2 --> 0.2 * 0.2 = 0.04
2 & 3 or 3 & 2 --> 0.02*2 = 0.04
3 & 3 --> 0.01

Adding all the probabilities up we get 0.06 + 0.04 + 0.01 = 0.15
Remember these questions are all about looking at the different possibilities.

Hope that helps!

Reply 383

QwertyG

9

Original post by Asyfa

3. When Rohit plays a game, the number of points he receives is given by the discrete
random variable X with the following probability distribution.
x 0 1 2 3
P(X = x) 0.4 0.3 0.2 0.1

Rohit can win a prize if the total number of points he has scored after 5 games is at least
10. After 3 games he has a total of 6 points.
You may assume that games are independent.
(e) Find the probability that Rohit wins the prize. (6mark)

can anyone help me on this ques?... its from jan 09 paper questionn 3 e

Rohit needs to get 4 or more points which can be obtained by getting a

1 3
3 1
2 2
3 2
2 3
3 3

You times em all up and add it and i think you get 0.15

Reply 384

otrivine

14

can someone explain to me how to do please the tree diagram in the jan 2011 paper that was confusing?

Reply 385

sl96

hey guys u know when we work out the median and the quartiles, do we hav to add 1 or round up, our school has confused me :s-smilie:

Reply 386

Asyfa

Original post by Gawjuz.x

I had the same problem with this question as well. This is how to tackle it:

Rohit can win a prize after 5 games the total number of points is 10. He has played 3 games so far and has scored 6 points.

3 games 6 points

This means in the 2 remaining games he needs to get ≥ 4

Let’s look at the possibilities:

1 & 3 or 3 & 1
Working out the probabilities (looking at your tables this would be) 0.03 * 2 = 0.06 (the reason that we multiply by 2 is there are two different permutations)

2 & 2 --> 0.2 * 0.2 = 0.04
2 & 3 or 3 & 2 --> 0.02*2 = 0.04
3 & 3 --> 0.01

Adding all the probabilities up we get 0.06 + 0.04 + 0.01 = 0.15
Remember these questions are all about looking at the different possibilities.

Hope that helps!

Yeah thank you so much! i get it now! :smile:

Reply 387

Asyfa

5. In a shopping survey a random sample of 104 teenagers were asked how many hours, to
the nearest hour, they spent shopping in the last month. The results are summarised in the
table below.
Number of hours Mid-point Frequency
0 – 5 2.75 20
6 – 7 6.5 16
8 – 10 9 18
11 – 15 13 25
16 – 25 20.5 15
26 – 50 38 10
A histogram was drawn and the group (8 – 10) hours was represented by a rectangle that
was 1.5 cm wide and 3 cm high.
(a) Calculate the width and height of the rectangle representing the group (16 – 25)
hours.

Im still confused abt how to work out the width and height from a histogram!!

Is there any other rule apart from

Freq density = freq/ class width

??

the mark scheme answer is

8-10 hours: width = 10.5 - 7.5 = 3 represented by 1.5cm
16-25 hours: width = 25.5 - 15.5 = 10 so represented by 5 cm
8- 10 hours: height = fd = 18/3 = 6 represented by 3 cm
16-25 hours: height = fd = 15/10 = 1.5 represented by 0.75 cm

(edited 11 years ago)

Reply 388

Jammy111

Can someone go through what the values for a and b mean in the regression line y=a+bd

Reply 389

arnab

11

Any help with part e of this question? I have no idea on how to do it.....

Uploaded with ImageShack.us

Reply 390

Jammy111

Original post by sl96

hey guys u know when we work out the median and the quartiles, do we hav to add 1 or round up, our school has confused me :s-smilie:

Same here, but I just never add one... when interpolating you just do n/2 and when finding quartiles, do n/2 also, if you get a whole number you find the mid point between that point and the next one, for example if you have 10 terms, 10/2=5, so you find the 5.5th term. If you have a decimal when dividing, you round up and fing that terms, for example if you have 11 terms, 11/2=5.5. so you find the 6th term.

Reply 391

otrivine

14

Original post by arnab

Any help with part e of this question? I have no idea on how to do it.....

Uploaded with ImageShack.us

what you do is from the table chose two values which equals to 4
so
3+1=4 so 0.3 x 0.1
1+3=4 so 0.1 x 0.3
2+2 =4 0.2 x 0.2
so then add them and get 0.1 :wink:

Reply 392

etansk

Original post by arnab

Any help with part e of this question? I have no idea on how to do it.....

Uploaded with ImageShack.us

It's asking which 2 X values add together to make 4, (1+3)(3+1)(2+2). Clearly that will be 2x P(X=1 x X=3) + P(X=2 x X=2)

So: 2(0.1x0.3) + (0.2x0.2) = 0.1

Reply 393

nibbles360

6

for part e)

you need X1 + X2 = 4
you have these possibilities:

probability
1+3 0.1x0.3
3+1 0.3x0.1
2+2 0.2x0.2

add those up and you get 0.1

Reply 394

007Shella

1

Crap I haven't started revision yet

*destined to fail*

Reply 395

When you see it...

16

Original post by aqua05

A couple of my mates told me.. is it true?

Original post by itsmehello

No they're harder than the edexcel papers

Wait I thought you were talking about the exam tomorrow! Like you had some inside information or something.
As for the SP papers, I personally find them easier, but many people find them harder. They are different to the past papers and probably won't be as good a preparation as doing actual past papers.

Reply 396

etansk

Original post by Asyfa

5. In a shopping survey a random sample of 104 teenagers were asked how many hours, to
the nearest hour, they spent shopping in the last month. The results are summarised in the
table below.
Number of hours Mid-point Frequency
0 – 5 2.75 20
6 – 7 6.5 16
8 – 10 9 18
11 – 15 13 25
16 – 25 20.5 15
26 – 50 38 10
A histogram was drawn and the group (8 – 10) hours was represented by a rectangle that
was 1.5 cm wide and 3 cm high.
(a) Calculate the width and height of the rectangle representing the group (16 – 25)
hours.

Im still confused abt how to work out the width and height from a histogram!!

Is there any other rule apart from

Freq density = freq/ class width

??

the mark scheme answer is

8-10 hours: width = 10.5 - 7.5 = 3 represented by 1.5cm
16-25 hours: width = 25.5 - 15.5 = 10 so represented by 5 cm
8- 10 hours: height = fd = 18/3 = 6 represented by 3 cm
16-25 hours: height = fd = 15/10 = 1.5 represented by 0.75 cm

Don't think so - but if you draw out both boxes next to each other, it becomes much easier to work out

Reply 397

jerichi

Someone please pretty please post the S1 Jan 2012 paper and mark scheme. I need it ASAP! :biggrin:

Reply 398

sl96

Original post by Jammy111

Same here, but I just never add one... when interpolating you just do n/2 and when finding quartiles, do n/2 also, if you get a whole number you find the mid point between that point and the next one, for example if you have 10 terms, 10/2=5, so you find the 5.5th term. If you have a decimal when dividing, you round up and fing that terms, for example if you have 11 terms, 11/2=5.5. so you find the 6th term.