You are Here: Home >< Maths

OCR MEI - S1 - 20th May 2015 watch

1. (Original post by yoomi)
Hey

I am just wondering how did u do the hypothesis test question !
The thing that confused me, that there wasn't p=0.78 in the table so could not finish my answer

Thank you
From what I remember:

Let p be the probability that a patient is cured with the drug
H0: p=0.78
H1: p>0.78

P(X=/>18) = P(X=19) + P(X=20)
= (20C19 * 0.78^19 * 0.22) + 0.78^20
= 0.0461 > 0.01
So not significant
So we accept H0 since there is insufficient evidence to suggest that the new drug cures a high percentage of patients.

Then next part: Sig level = 5%
so same calculations then
= 0.0461 < 0.05
So inversed conclusion to previous part.

Hope this helped!
2. (Original post by joe12345marc)
Even then, you can't do binomial distribution probablity unless you have a number of total trials, i.e (3C2) but there's no total, so it can't be done using P(X>....) etc
P(>2) has nothing to do with the binomial distribution, it's just notation.

The question coyld easily be interpreted in two ways so arguing about it is moot. I do think the answer OCR wanted is 3/38 (I got 1/57), but w/e. Screw them for wording it so ambiguously :P
3. (Original post by Duskstar)
P(>2) has nothing to do with the binomial distribution, it's just notation.

The question coyld easily be interpreted in two ways so arguing about it is moot. I do think the answer OCR wanted is 3/38 (I got 1/57), but w/e. Screw them for wording it so ambiguously :P
I agree. They may withhold losing marks for either tbh, as clearly it will be very close to 50:50 split - even from high scoring candidates.

If he got Cherry Cherry Cherry other , you could say "It took him MORE THAN 2 chocolates BEFORE he got on he liked"
If he got Cherry Cherry other , you could say "It took him more than 2 chocolates before getting one he liked"

Same sentence, different emphasis so different meaning
4. (Original post by MathsMaestro)
Hypothesis test:

X~B(20, p)
p is the probability that a random person in the population will be treated for a minor illness.
Should p not be the probability a randomly selected person is cured ?
5. (Original post by jonnyiw)
Should p not be the probability a randomly selected person is cured ?
I think that's what they meant.
6. (Original post by Duskstar)
I think that's what they meant.
Yeah they probably did but the mei examiner is very unforgiving for those type of things
7. (Original post by Qwertykeyboard15)
I think the last question said about him picking out more than 2 of the ones he doesn't like before he has a chocolate he does like.
This means that he could have had 2 cherries, 3 cherries etc up to all 6 cherries before eating one that he likes.
So you start with 6/20 x 5/19 x 14/18 (that's the probability of now picking one he likes) and then you do it again but with 3 cherries, then 4, 5, and 6
No becauseI believe the q said "prob. of him having to eat more than 2 before finds one he likes". it may be that he picks all 6 cherry ones before he finds one he doesn't like, we don't know. It just asks you to find the probability of him not getting one he likes from the first 2 (i.e. 2 cherries).
8. (Original post by lilmi5s_elmo)
No becauseI believe the q said "prob. of him having to eat more than 2 before finds one he likes". it may be that he picks all 6 cherry ones before he finds one he doesn't like, we don't know. It just asks you to find the probability of him not getting one he likes from the first 2 (i.e. 2 cherries).
Yes you're correct, nice to see someone here understands.
9. If I rounded the last answer to 0.079 which is roughly equivalent to 3/38 will I pick up full marks on that Q?
10. (Original post by Tee546)
If I rounded the last answer to 0.079 which is roughly equivalent to 3/38 will I pick up full marks on that Q?
You'd be very unlucky to lose a mark, but don't discount it as I'm sure you know S1 mark schemes are by far the most stupid. You should be completely fine, it's 3.d.p and entirely correct so unless the exam was found ridiculously easy and they need to invent new ways to make us lose marks, you'll be absolutely fine!
11. (Original post by joe12345marc)
You'd be very unlucky to lose a mark, but don't discount it as I'm sure you know S1 mark schemes are by far the most stupid. You should be completely fine, it's 3.d.p and entirely correct so unless the exam was found ridiculously easy and they need to invent new ways to make us lose marks, you'll be absolutely fine!
Nice one, cheers! I had an absolute nightmare with the easiest question on the paper: the on with the deck of cards and aces. I did 1- P(ace then ace), will I get a follow through mark using that answer for my expectation?
12. (Original post by yoomi)
Hey

I am just wondering how did u do the hypothesis test question !
The thing that confused me, that there wasn't p=0.78 in the table so could not finish my answer

Thank you
The key was to do an individual binomial distribution for both 19 and 20 and add them together which was part of the working out for the previous question. This came to 0.046 which is 4.6% which means not sufficient evidence to reject null hypothesis, then the next question asked what if it was done at 5% significance level which would be it was sufficient evidence to reject null hypothesis because 4.6 is less than 5 I'm not sure if this was the correct way to do it but I came out with the right answer.
13. (Original post by Tee546)
Nice one, cheers! I had an absolute nightmare with the easiest question on the paper: the on with the deck of cards and aces. I did 1- P(ace then ace), will I get a follow through mark using that answer for my expectation?
I'm sorry I do not remember the question, any context please? Sorry

Edit: You usually do get 1 FT mark for expectation, BUT NOT ALWAYS so not sure :/
14. (Original post by joe12345marc)
I'm sorry I do not remember the question, any context please? Sorry

Edit: You usually do get 1 FT mark for expectation, BUT NOT ALWAYS so not sure :/
When you had to work out the probability of neither card being an ace?
15. (Original post by Tee546)
When you had to work out the probability of neither card being an ace?
You'd almost certainly get a follow through mark for working out expectation as long as you did it with your own answer
16. Is there an unofficial mark scheme for this paper anywhere?
17. (Original post by princessliz)
Is there an unofficial mark scheme for this paper anywhere?
Page 11 iirc
18. (Original post by thecalmmorning)
I had no idea how to do that
I've no idea howitzer guessed it but I just did 1-(5/6)^3 on my calculator and got 91/216.... It was a miracle
19. I'm sorry i cant finnd it
(Original post by Duskstar)
Page 11 iirc
20. (Original post by princessliz)
I'm sorry i cant finnd it
It was page 13:

(Original post by otherdan)
here ~

Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: May 24, 2016
Today on TSR

Edexcel C3 Maths Unofficial Markscheme

Find out how you've done here

1,176

students online now

800,000+

Exam discussions

Poll
Useful resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE