You are Here: Home >< Maths

# OCR (non mei) S2 Wednesday 15th June 2016

Announcements Posted on
Would YOU be put off a uni with a high crime rate? First 50 to have their say get a £5 Amazon voucher! 27-10-2016
1. can someone show how you do question 5i
2. (Original post by arronpile)
I got up to O~=0.03/1.645 how many marks out of 6 do you think I got
About 3, you did half of the question right so half marks dropped I'd say.
3. (Original post by arronpile)
can someone show how you do question 5i
H0: p = 0.55
H1: p > 0.55

G~B(8,0.55)
P(G>=6) = 1 - P(G<=5) = 1-0.7799 = 0.2201

As 22.01% > 10%, accept H0.
4. (Original post by tinkerbella~)
H0: p = 0.55
H1: p > 0.55

G~B(8,0.55)
P(G>=6) = 1 - P(G<=5) = 1-0.7799 = 0.2201

As 22.01% > 10%, accept H0.
p(G>6)=1-P(G<or equal to 6) isn't that right??
5. (Original post by arronpile)
p(G>6)=1-P(G<or equal to 6) isn't that right??
But you want P(G>=6), you test for the probability of getting the test statistic or a more extreme value.
6. (Original post by tinkerbella~)
But you want P(G>=6), you test for the probability of getting the test statistic or a more extreme value.
I did it for P(G>6) so how many marks you think I dropped
7. (Original post by arronpile)
I did it for P(G>6) so how many marks you think I dropped
Honestly I have no idea sorry! Somebody else on here might have a clue though
8. (Original post by arronpile)
I did it for P(G>6) so how many marks you think I dropped
Somewhere between 2-4 marks, probably 2 or 3 because it still gives you the same conclusion.
9. Did you have to multiply the sample variance by n/n-1 in 8ii?
Did you have to multiply the sample variance by n/n-1 in 8ii?
Yes
11. Any idea what the mark distribution is for 8ii)? I forgot to work out the actual population variance but worked out that it if it was greater than 12.45 it would result in Ho being accepted... I'm worried that I'll lose all/most the marks though
12. (Original post by rtycoss)
Any idea what the mark distribution is for 8ii)? I forgot to work out the actual population variance but worked out that it if it was greater than 12.45 it would result in Ho being accepted... I'm worried that I'll lose all/most the marks though
5 marks.
13. so for Q8 I did part i in part ii and in part i I just did it without dividing by 50. Got the last part right, got the ho/1, any chance I'll get the marks for doing part i in ii? How many marks should I get over the Q??
Any help is appreciated
14. (Original post by TheNicholas)
so for Q8 I did part i in part ii and in part i I just did it without dividing by 50. Got the last part right, got the ho/1, any chance I'll get the marks for doing part i in ii? How many marks should I get over the Q??
Any help is appreciated
For using the wrong variance on part i) You will probably lose 2 accuracy marks and the conclusion because the conclusion is usually dependent on the correct value.
For ii) I have no idea.
15. (Original post by WorkHardGoToUni)
For using the wrong variance on part i) You will probably lose 2 accuracy marks and the conclusion because the conclusion is usually dependent on the correct value.
For ii) I have no idea.
16. (Original post by xsanda)
Xsanda's solutions

1) Unbiased mean and variance of summarised data
E(V) = 268
Var(V) = 1912/13 = 147 [4]

2) Normal distribution, given P(M<1.00) = 5%
P(M>1.05) = 13.6% [6]

3) Approximated binomial
n large, np = 26 > 5, nq = 14 > 5
use normal distribution
P(X<=30) = 0.932 [7]

4) Poisson, P(X=4) = P(X=5)
λ = 5, P(X=5) = 0.175 [5]

5) School with 55% girls
i) P(G≥6) = 22% (above significance level), do not reject H₀ [7]
ii) Fixed prob of girl chosen, independent of previous Head Students [1]

6) Cars along a narrow road
i) Constant probability of cars throughout the minute, cars independent [2]
ii) λ = 6.5, P(4≤X<7) = 0.561[3]
iiia) N(30,30)
P(X>35) = 0.158 [6]
b) Not independent (narrow, slow road, so affected by car in front) [1]

7) Probability density function
i) x is a single sample value of X [1]
ii) a=1, b=1.5 [7]
iii) E(X) = 7/4 = 1.75 [3]

8) Animals dying at zoo
i) P(L<12.48) = 4.88% < 5%
reject H₀, substantial evidence zoos limit life expectancy [7]
ii) s² = 12.5
5.05% > 5%, do not reject H₀, insufficient evidence zoos limit life expectancy [5]
iii) yes, as the distribution of the original data is not given [1]

9) Poisson test, λ=11
i) reject if P(R≥20)
92% chance of Type II error [6]
I did 8i and ii completely correctly but just the wrong way around. I used 12.5 for i and 12.25 for ii... How many marks u reckon worst case I could have lost out of 12??? .. part i being worth 7 and part ii being worth 5. Thanks
17. (Original post by TheNicholas)

i did the same how many marks do you think we'll lose?
18. (Original post by Yazmin123)
i did the same how many marks do you think we'll lose?
Considering we got iii right, I'd say anywhere from 6-11
19. can someone please explain the steps to get the answer to q8ii
20. (Original post by nao9)
can someone please explain the steps to get the answer to q8ii
Use the n/(n-1) formula to calculate an unbiased estimate of the population variance from the sample variance. Then carry out the hypothesis test just like in part (i).

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: July 12, 2016
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:
Today on TSR

### University open days

Is it worth going? Find out here

Poll
Useful resources