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# OCR MEI - S1 - 20th May 2015 watch

1. Does anyone have the mark scheme of last years exam? Thanks!
2. (Original post by ¡Muy bien!)
Does anyone have the mark scheme of last years exam? Thanks!
http://vle.woodhouse.ac.uk/topicdocs.../S12014May.pdf
3. Thanks!
4. (Original post by DashDotDotDash)
Does anyone have any good sources for revision on this exam?
I'm retaking this exam from last year and I honestly cannot remember any of it. I fine that overall MEI OCR Maths doesn't have enough resources anyway, let alone anything that isn't Core _..
1) http://furthermaths.org.uk/mei-revision
2) http://www.examsolutions.net/maths-r.../S1/module.php
5. (Original post by Manexopi)
Im confused with critical region like sometimes they do both lower and upper tail and sometimes just the upper? Like how do ik when to do what?
Summed up:
If p > 0.5 then compare to high tail of critical region (trial & error)
if p < 0.5 then compare to low tail of critical region (both have to be below it)
Written more on post above mate
6. Hi,
I was just wondering whether somebody could give me an explanation of this question on last years paper

4)i There are 16 girls and 14 boys in a class. Four of them are to be selected for a quiz team the team is to be selected at random.

i) Find the probability that all 4 members of the team will be girls
ii) Find the probability that the team will contain at least one girl and at least one boy

Thanks
7. (Original post by CallumCC)
Hi,
I was just wondering whether somebody could give me an explanation of this question on last years paper

4)i There are 16 girls and 14 boys in a class. Four of them are to be selected for a quiz team the team is to be selected at random.

i) Find the probability that all 4 members of the team will be girls
ii) Find the probability that the team will contain at least one girl and at least one boy

Thanks
Hey!

I think you do it like this:

i) 16/30 x 15/29 x 14/28 x 13/27 =

As there are 30 people, 16 of which are girls

ii) 1- (probability of all girls (which you just worked out in (i)) + probability of all boys)

hope that helps let me know if you want more detail
8. Can someone help me with hypothesis testing and significance levels please

Say you are given a 5% sig level, if your probability is 0.052 for example, does that mean it is out of the significance level or in the significance level, and Ho is accepted right?

thanks
9. (Original post by alipx)
Hey!

I think you do it like this:

i) 16/30 x 15/29 x 14/28 x 13/27 =

As there are 30 people, 16 of which are girls

ii) 1- (probability of all girls (which you just worked out in (i)) + probability of all boys)

hope that helps let me know if you want more detail
Thanks very much
I understand the first part now,
sorry but if you don't mind could you explain the second part a bit more, this is the topic i'm really not keen on, do you know the exact topic this is testing

Cheers
10. Since it asked for the probability that there is at least 1 girl and at least 1 boy, you can work out the probability this is false. That means it's all girls or all boys. That's what he did here and then did 1 - Ans to get the value for there being at least 1 of each.
Hope that explains.
11. (Original post by CallumCC)
Thanks very much
I understand the first part now,
sorry but if you don't mind could you explain the second part a bit more, this is the topic i'm really not keen on, do you know the exact topic this is testing

Cheers
no probs!

I think it's just part of probability, I'm not good on the topic names

ii) You need to find the probability of having at least one girl and one boy.
You could do this the long way
i.e girl, girl, girl, boy
girl, girl, boy, boy
girl, boy, boy, boy
until you have all the options but this would take ages

But we know that probabilities always equal 1, (I'm gonna go on a bit of a tangent here but bear with) for example if you want to find the probability of getting tails if you flip a coin and you know the chances of heads is 0.5, you can work it out by doing 1 - 0.5 to get 0.5 right?

So here we are doing the same, we are taking away what it cannot be (in this case all girls and all boys because then we cannot have one of each). This is much quicker especially because we have already worked out the prob of all girls in part i

did that help? It's hard to word haha
12. (Original post by alipx)
no probs!

I think it's just part of probability, I'm not good on the topic names

ii) You need to find the probability of having at least one girl and one boy.
You could do this the long way
i.e girl, girl, girl, boy
girl, girl, boy, boy
girl, boy, boy, boy
until you have all the options but this would take ages

But we know that probabilities always equal 1, (I'm gonna go on a bit of a tangent here but bear with) for example if you want to find the probability of getting tails if you flip a coin and you know the chances of heads is 0.5, you can work it out by doing 1 - 0.5 to get 0.5 right?

So here we are doing the same, we are taking away what it cannot be (in this case all girls and all boys because then we cannot have one of each). This is much quicker especially because we have already worked out the prob of all girls in part i

did that help? It's hard to word haha
What he said
13. (Original post by alipx)
Can someone help me with hypothesis testing and significance levels please

Say you are given a 5% sig level, if your probability is 0.052 for example, does that mean it is out of the significance level or in the significance level, and Ho is accepted right?

thanks
5.2% > 5% so you are not in the Critical Region... so accept Ho
14. (Original post by alipx)
no probs!

I think it's just part of probability, I'm not good on the topic names

ii) You need to find the probability of having at least one girl and one boy.
You could do this the long way
i.e girl, girl, girl, boy
girl, girl, boy, boy
girl, boy, boy, boy
until you have all the options but this would take ages

But we know that probabilities always equal 1, (I'm gonna go on a bit of a tangent here but bear with) for example if you want to find the probability of getting tails if you flip a coin and you know the chances of heads is 0.5, you can work it out by doing 1 - 0.5 to get 0.5 right?

So here we are doing the same, we are taking away what it cannot be (in this case all girls and all boys because then we cannot have one of each). This is much quicker especially because we have already worked out the prob of all girls in part i

did that help? It's hard to word haha
Thanks so much

Just saved me for tomorrow
15. (Original post by the bear)
5.2% > 5% so you are not in the Critical Region... so accept Ho
Thank you!!

Also if it's a two tailed test you halve it right? So 2.5% at each end for example?
16. (Original post by CallumCC)
Thanks so much

Just saved me for tomorrow
Anytime I hope it's a nice paper
17. (Original post by alipx)
Thank you!!

Also if it's a two tailed test you halve it right? So 2.5% at each end for example?
yes, exactly.
18. (Original post by the bear)
yes, exactly.
yay thank you
19. Do you ever do strict inequalities for hypothesis when carrying out the test? Or is it always greater than or equal to or less than or equal to?
20. Can anyone explain central tendency to me please?
thanks

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