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AQA A2 Statistics 2 MS2B Unofficial Mark Scheme

Poll

What do you think will be the raw mark for an A* (90UMS)

These are my answers from the Statistics 2 exam this morning :smile:

Hope it went well!
1. Poisson Distribution
a) P(X=<5) = 0.935 (2 Marks)
b) P(X=2) = 0.119 (3 Marks)
c) Parameter/Mean = 15
P(12 =< X <18) => P(X=< 17) - P(X=<11) = 0.564 (4 Marks)
2. Rectangular Distribution
a) k=b-a (1 Mark)
b) i) a=-2 b=4 (4 Marks)
ii) Out of 4, the probability of one being negative can be calculated using binomial
= 4C1 * (1/3) * (2/3)^3 = 0.395 (3 Marks)
3.
a)
i) Assuming that the standard deviation is 2 => Use Z value to calculate confidence interval = (907.7, 910.7) (4 Marks)
ii) As the standard deviation is unknown, use s as an unbiased estimate for the standard deviation => Use T to calculate the confidence interval = (907.2, 911.2) (4 Marks)
b) Inspector has a concern about weight of bags being less than 907 (2 Marks)
4. a) No (1 Mark)
b) Reject the H0, Mean is less than 44.1 (8 Marks)
c) i) Explain Type 1in context (2 Marks)
ii) explain Type 2 in context
5.
a) Chi-Squared = 7.053, 7.053>5.991 so Reject H0 (9 Marks)
b) The belief is likely correct (1Mark)
6.
a) 0.17 (2 Marks)
b) Show f(x) = (1/2) - (1/8)x (1 Mark)
c) i) E(X) = 4/3 (3 Marks)
ii) E(X^2) = 8/3 => Var(X) 8/9 (4 Marks)
d) E(Y) = 2 Var(Y) = 8 (2 Marks)
7.
a) show a=0.180 using Poisson Distribution, and b=0.143 as the sum of all the probabilities = 1 (3 Marks)
b) E(X) = 2.925 E(X^2) = 10.113 => SD = 1.25 (5 Marks)
c) 1.89 pounds (2 Marks)
d) Using 4 => 2.17 pounds, therefore more profit will be made by stocking 4 (5 Marks)

Credit to Lau14 for Mark Allocations :smile:

(edited 8 years ago)

Scroll to see replies

Reply 1

a123a

What do think the grade boundaries will be? Do you agree that this was harder than last year? I think so.

Reply 2

jjsnyder

Original post by a123a

What do think the grade boundaries will be? Do you agree that this was harder than last year? I think so.

I think it was harder, not sure what the boundaries will be, but I am pretty certain they will be lower than last years :smile:

Reply 3

a123a

Original post by jjsnyder

I think it was harder, not sure what the boundaries will be, but I am pretty certain they will be lower than last years :smile:

I would hope so!

Reply 4

Red Fox

6b was show f(x) = blah blah from F(x)

Reply 5

jjsnyder

Original post by Red Fox

6b was show f(x) = blah blah from F(x)

Thanks

Reply 6

majka

I think that it was harder!

How many ums do you think will 56 be?

Reply 7

jjsnyder

Original post by majka

I think that it was harder!

How many ums do you think will 56 be?

I of course cannot tell you for certain, but probably about 72 UMS

4b?

Original post by majka

I think that it was harder!

How many ums do you think will 56 be?

Likely around the 70 region, S2 usually has fairly high boundaries and while they should be lower than last year I don't know that they'll drop massively!