OCR MEI - S1 - 20th May 2015

Does anyone have the mark scheme of last years exam? Thanks!

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 _..

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?

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

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

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

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

5.2% > 5% so you are not in the Critical Region... so accept H_o

Thanks so much

Just saved me for tomorrow

Thank you!!

Also if it's a two tailed test you halve it right? So 2.5% at each end for example?

yes, exactly.