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# Quantitative methods course question.

Maths and statistics discussion, revision, exam and homework help.

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1. (Original post by SpiggyTopes)
For the last question, there are 10 batteries which are made by company AND are faulty, you have counted these twice when fining your total number of batterries which are made by company A and are faulty.

I hope they help and please ask me as many as you like!

You do a lot of probability don't you!!
Please make your explanation on the battery question more clearer in a way that I can see the question from the same perspective you see it from, and I can understand fully the reasoning you are applying. Please explain the theory in detail.

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2. (Original post by SpiggyTopes)
For the last question, there are 10 batteries which are made by company AND are faulty, you have counted these twice when fining your total number of batterries which are made by company A and are faulty.

I hope they help and please ask me as many as you like!

You do a lot of probability don't you!!
Thank you for your help. But, can you scan the lower part of the computer and telephone question again ? (iii) is cut, so I can't read what you've written. Alternatively, you can type that part instead of scanning it again. Than you.

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3. Re: Quantitative methods course question.
(Original post by gabriel 41)
Please make your explanation on the battery question more clearer in a way that I can see the question from the same perspective you see it from, and I can understand fully the reasoning you are applying. Please explain the theory in detail.

This was posted from The Student Room's iPhone/iPad App
There are 150 batteries made by company A and there are 20 faulty batteries. However, 10 of these faulty batteries are ALSO made by company A, and we can't count them twice! Therefore there are 160 batteries that can be chosen and fulfil the criteria, not 170 as you thought.

(Original post by gabriel 41)
Thank you for your help. But, can you scan the lower part of the computer and telephone question again ? (iii) is cut, so I can't read what you've written. Alternatively, you can type that part instead of scanning it again. Than you.

This was posted from The Student Room's iPhone/iPad App
It says: Here, you only consider those who use a telephone (100 People). 70 of these 100 people don't use a computer so the answer is 70/100, or 7/10, or 0.7.

Ask me as many questions as you wish!!!
4. Re: Quantitative methods course question.
(Original post by gabriel 41)
Okay there's no problem. I get you well. You've been so nice helping me around. I hope I'm not too annoying but I have another question that I would like you to help me in. This question is on probability and here's the question:

Q8 (a) An inspection carried out on 300 electronic items manufactured by two companies
(Company A and Company B) found that 30 were faulty. Of the 150 electronic
items inspected that were manufactured by Company A, 10 were found to be faulty.
In contrast, 20 were found to be faulty out of the 150 inspected electronic items
manufactured by Company B.
If one electronic item is randomly selected from these 300 electronic items, fi nd the
probability that this electronic item is:
(i) Manufactured by Company B; (3 marks)
(ii) Faulty; (3 marks)
(iii) Not faulty and is manufactured by Company B; (4 marks)
(iv) Manufactured by Company A, given that it is faulty. (4 marks)

So (i) and (ii) are very easy and I'm okay there but (iii) and (iv) is giving me the problem. I like solving probability questions using venn diagrams, and I've attached my venn diagram, see below. This venn diagram is my answer to (iii) and (iv). From my venn diagram you can see that (P) of faulty and manufactured by company B (answer to (iii)) is 20/300, so (P) of not faulty and manufactured by company B will be 1-(20/300) which is 14/15. However, this answer seems to be wrong and the mark schemes shows (P) of this question as 13/30. Isn't my method correct. What's the problem. And then for (iv) (P) of manufactured by A and faulty, from my venn diagram is 10/300 which is 1/30 but in the mark scheme the (P) of this question is (1/3). I think for (iv) the mark scheme is wrong. What do you think? Please help me. Thank you for your time and co-operation.
The above question is question 8 part (a) but I'm also totally stuck in question 8 part (b). I've got no idea in question 8 part (b) and we've never dealt with such probability question in class, so I'm totally lost on what to do. You need to explain to me this question as if I'm learning from you the first time, as a beginner. Also, I've attached the standard normal distribution formula sheet that we get in an exam and along with that I've attached the answer to the question too. Please find them attached.
Attached Thumbnails

Last edited by gabriel 41; 25-07-2012 at 19:36.
5. Re: Quantitative methods course question.
(Original post by gabriel 41)
The above question is question 8 part (a) but I'm also totally stuck in question 8 part (b). I've got no idea in question 8 part (b) and we've never dealt with such probability question in class, so I'm totally lost on what to do. You need to explain to me this question as if I'm learning from you the first time, as a beginner. Also, I've attached the standard normal distribution formula sheet that we get in an exam and along with that I've attached the answer to the question too. Please find them attached.
Sorry, but my maths option is mechanics and not statistics so I have only ever done standard deviation in biology so I'm not very confident on it.
6. Re: Quantitative methods course question.
Can someone please answer the above question for me. The question is in the post of number 24. Please find the question, answers and formula sheet attached, and assist me in this question.

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Last updated: July 27, 2012
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