OCR (non mei) S2 Wednesday 15th June 2016

I got up to O~=0.03/1.645 how many marks out of 6 do you think I got

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 H_0.

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.

I did it for P(G>6) so how many marks you think I dropped

I did it for P(G>6) so how many marks you think I dropped

Did you have to multiply the sample variance by n/n-1 in 8ii?

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

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.

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]

Thank you for your reply

i did the same how many marks do you think we'll lose?

can someone please explain the steps to get the answer to q8ii