Edexcel S4 - 28th June 2017

Thanks once again, you've helped me alot! Just one more which I really cant get my head around, http://pmt.physicsandmathstutor.com/download/Maths/A-level/S4/Papers-Edexcel/June%202013%20QP%20-%20S4%20Edexcel.pdf part f. Thank you!!!

edit:5f

So you're given that it takes 20 mins to collect a 20ml sample so this is always the length of time the scientist takes as they always take a 20ml sample. Then you are given that it takes 15 mins to collect a 10 ml sample. The statistician will either take 1 or 2 10ml samples so the expected time for the statistician will be 15*Probability of taking 1 sample + 30*Probability of taking 2 samples. Now she only needs to take 1 sample if there are 2 or more or 0 organisms present as she then immediately forms her conclusion. However if 1 organism is present she will take a 2nd sample but no more after this. This gives her expected time as 15 * P(X is not 1) + 30 * P(X=1). This will give you something in terms of lambda. You can then just set this as greater than 20 and manipulate the inequality to get the result.

Thank you so much, I feel so much more confident about tomorrow. Best of luck, but I'm sure you won't need it lol.

That was a fairly standard paper tbh

I think I got 8.8, 30.2 for confidence interval, (X1(X1-1) + X2)/n^2 for unbiased estimator of p^2, a and b are 0.5 can't really remember anything else haha

I think I got a critical region of X>10

I got X1(X1-1)/n(n-1) for the unbiased estimator. others are the same.

Some other answers I remember.
1. both not significant
2.C.R. X>=11 Type I 0.0426
9 not in the C.R.
Type II 0.8159
3. Reject
C.I for the variance (4.22, 56.3)
4. in pairs
differences normally distributed
5. (8.79, 30.2)
6. a=b=0.5
bias is Var(p) (2a^.......

Anyone agrees??????

I put same sample size for the pairs one you think that'd be fine?
What was question 3 again?

I put same sample size for the pairs one you think that'd be fine?
What was question 3 again?

I got X1(X1-1)/n(n-1) for the unbiased estimator. others are the same.

Some other answers I remember.
1. both not significant
2.C.R. X>=11 Type I 0.0426
9 not in the C.R.
Type II 0.8159
3. Reject
C.I for the variance (4.22, 56.3)
4. in pairs
differences normally distributed
5. (8.79, 30.2)
6. a=b=0.5
bias is Var(p) (2a^.......

Anyone agrees??????

Do you agree with all others

Yeah it looks like i got the same as you for everything except the last part for the unbiased estimator I didn't find that question.

For the variances of Jam did you use simultaneous equations and find 19.5 as the difference of the means with t-test 28 degrees of freedom

Oh I never thought of doing X1(X1 - 1)/n(n-1) do you think I'd still get the mark because my expected value is still p^2?

But yeah I agree with all of the others

last two parts of last q seemed tricky compared to normal

when you found E[p-hat^2] did you find it in terms of a and b or did you sub the values a=b=1/2 ?

the algebra seemed too unfriendly w/ the a's and b's.

Don't think simul equations are needed.
Simply find the variance for J and then do the pooled variance.....etc.

How did you find the variance for J without doing simultaneous equations?

did you find something like 2.0803