Don't understand the process of this stats question Watch

OJ Emporium
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#1
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"A factory buys 10% of its components from supplier A, 30% from supplier B and the rest from supplier C. It is known that 6% of the components it buys are faulty.

Of the components bought from supplier A, 9% are faulty and of the components bought from supplier B, 3% are faulty.

a) find the percentage pf the components bought from supplier C that are faulty

A component is selected at random
b) Explain why the event 'the component was bought from supplier B' is not statistically independent from the event 'the component is faulty'."

So what my issue is, is that I don't understand the process behind these questions. I was thinking it had something to do with Binomial Distribution and etc. but still didn't understand on how I could actually apply it to this question.
It would really help on finding out how I can answer questions like these in the future, thanks.
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Muttley79
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(Original post by OJ Emporium)
"A factory buys 10% of its components from supplier A, 30% from supplier B and the rest from supplier C. It is known that 6% of the components it buys are faulty.

Of the components bought from supplier A, 9% are faulty and of the components bought from supplier B, 3% are faulty.

a) find the percentage pf the components bought from supplier C that are faulty

A component is selected at random
b) Explain why the event 'the component was bought from supplier B' is not statistically independent from the event 'the component is faulty'."

So what my issue is, is that I don't understand the process behind these questions. I was thinking it had something to do with Binomial Distribution and etc. but still didn't understand on how I could actually apply it to this question.
It would really help on finding out how I can answer questions like these in the future, thanks.
Have you done part (a)? Try that first.
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OJ Emporium
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(Original post by Muttley79)
Have you done part (a)? Try that first.
I don't wanna come off as a prick but that's a yikes from me man

Like I don't know how to do the question man
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Muttley79
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(Original post by OJ Emporium)
I don't wanna come off as a prick but that's a yikes from me man

Like I don't know how to do the question man
What % are bought from C?

Overall 6% are faulty so we need to find what % of those bought fromC will give overall 6% faulty.

10% bought from A 9% faulty .... overall prob of a fautly ones from A is?
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begbie68
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(Original post by OJ Emporium)
I don't wanna come off as a prick but that's a yikes from me man

Like I don't know how to do the question man
Hopefully, you'll know how to make a tree-diagram?

You've been given, in words, the majority of the probabilities to fit onto each branch, and you will be able to calculate the missing values (again, from the given info)
This should lead to tha answer for part a

For part b, you'll need to know the rule for independent events.
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Phoebe Jones
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create a tree diagram
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OJ Emporium
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Apologies for the late reply
I made a 3-way tree diagram with:

Supplier A on top (10%) - 9% Faulty, 91% normal
Supplier B in the middle (30%) - 3% Faulty, 97% normal
Supplier C on the bottom (60%) - x% faulty, (100-x)% normal

So apparently this "adds up" to an overall 6% and I'm overall confused on how that works unless I (obviously) am missing something.
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DFranklin
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(Original post by OJ Emporium)
Apologies for the late reply
I made a 3-way tree diagram with:

Supplier A on top (10%) - 9% Faulty, 91% normal
Supplier B in the middle (30%) - 3% Faulty, 97% normal
Supplier C on the bottom (60%) - x% faulty, (100-x)% normal

So apparently this "adds up" to an overall 6% and I'm overall confused on how that works unless I (obviously) am missing something.
I suggest you imagine that you have 1000 components being supplied.

If 6% are faulty, how many components is that?
Then, how many components will be supplied by A? And how many of these will be faulty?
Same for B.
So how many faulty components must come from C? And how many components must come from C? So the percentage is?
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Mr_Mysterious
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was the answer to part a 6%
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