a level aqa practice paper 3 set 2 help

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gibsh
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Hi everyone , have been struggling to complete a couple of statistics question on the paper,could someone help me out please?
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briteeshbro
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(Original post by gibsh)
Hi everyone , have been struggling to complete a couple of statistics question on the paper,could someone help me out please?
Which questions?
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gibsh
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the whole of question 19
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(Original post by briteeshbro)
Which questions?
(Original post by gibsh)
the whole of question 19
can you help me please ?
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briteeshbro
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for a i you form two equations using their respective z values and the equation to standardise z values. You solve these simultaneously.
for ii you use the p value of 0.15 given in the question stem to from a binomial distribution with n being 8.
for b you calculate the respective probabilities using the distributions the question has stated, and multiply them together (they threw in a bit of conditional probability chapter in this question)
In further maths, when we combine 2 normal distributions, one of the conditions has to be that they're independent of each other, which is leading me to think that's the answer for part c. However, that is indeed Fmaths and might not apply to a level and the way we combine them is a bit different. That being said, I believe the logic still follows through, therefore, that's the answer I would have put.

(Original post by gibsh)
can you help me please ?
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gibsh
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(Original post by briteeshbro)
for a i you form two equations using their respective z values and the equation to standardise z values. You solve these simultaneously.
for ii you use the p value of 0.15 given in the question stem to from a binomial distribution with n being 8.
for b you calculate the respective probabilities using the distributions the question has stated, and multiply them together (they threw in a bit of conditional probability chapter in this question)
In further maths, when we combine 2 normal distributions, one of the conditions has to be that they're independent of each other, which is leading me to think that's the answer for part c. However, that is indeed Fmaths and might not apply to a level and the way we combine them is a bit different. That being said, I believe the logic still follows through, therefore, that's the answer I would have put.
I ll do that but is it ok for you to check my work after I have done it?Would really appreciate that.
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briteeshbro
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(Original post by gibsh)
I ll do that but is it ok for you to check my work after I have done it?Would really appreciate that.
yhhh sure
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gibsh
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(Original post by briteeshbro)
yhhh sure
hey is it normal that i got a negative standard devviation?
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briteeshbro
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(Original post by gibsh)
hey is it normal that i got a negative standard devviation?
No, it isnt.
My instinctive feeling is that you entered the wrong values into ur inverse normal. On the classwiz, it gives proabalities in the form P(Z<z), so you would need to enter 0.85 and 0.2 respectively into the inverse normal for the values to match since the sign in both the probabilities at the start is >.
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gibsh
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yes you were right but you know for (ll) i got probability equals to 0.
It feels wrong
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(Original post by gibsh)
yes you were right but you know for (ll) i got probability equals to 0.
It feels wrong
n is the number of trials in Binomial right? So why would you test for the probability of getting more than 65 then the total number of trials is 8? You get 0 because there is no chance that he sells more than 65 litres on 65 out of 8 days. The question says at least 3 days so the probability you should be calculating is P(X>=3)
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gibsh
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So i got n being 8 and p being 0.15.
Did (X≥3)=1-(X≤2) WHICH gave me 0.02136
I m assuming that is correct ?
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gibsh
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(Original post by gibsh)
You know for part b do i have to standirdize the t-N(1.6,0.4) and C-N(6.5,1.4) AND then do normal distribution or plug the values in the calculator straight away?
(Original post by briteeshbro)
n is the number of trials in Binomial right? So why would you test for the probability of getting more than 65 then the total number of trials is 8? You get 0 because there is no chance that he sells more than 65 litres on 65 out of 8 days. The question says at least 3 days so the probability you should be calculating is P(X>=3)
You know for part b do i have to standirdize the t-N(1.6,0.4) and C-N(6.5,1.4) AND then do normal distribution or plug the values in the calculator straight away?
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I would plug them in straight away. I'm not sure how you could get the necessary values by standardising. Wouldnt that take you round in a circle?
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(Original post by briteeshbro)
I would plug them in straight away. I'm not sure how you could get the necessary values by standardising. Wouldnt that take you round in a circle?
is this correct?
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Looks right
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gibsh
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(Original post by briteeshbro)
Looks right
Could you chech my work and help me out on 15b and 16 ?
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