192 replies to this topic

[Qbix]

b is correct I would say.
i doubted about a as well

[MdaG]

Qbix, on Nov 14 2005, 10:53 PM, said:

b is correct I would say.
i doubted about a as well

Explain how you came to your answer on b?

[Qbix]

exactly 2 events:
the sum of
(not a) * b * c
a *(not B) *c
a*b*(not c)

[MdaG]

Qbix, on Nov 14 2005, 10:56 PM, said:

exactly 2 events:
the sum of
(not a) * b * c
a *(not *c
a*b*(not c)

That's correct, but I think you must've made some error along the way. It's suppose to be 0.306. Still, it's correct. Now only a is left

[A. J. Raffles]

*makes another random guess* 0.838

[BeefontheBone]

That's no random guess! You big fibber.

Should be 1-(probability that none occur) which is equal to 1-(0.9*0.6*0.3) which I think is indeed .838. Incidentally, why doesn't the calculator in Windows have a "insert previous answer" button like any calculator worth buying?

[A. J. Raffles]

Curses! I've given myself away! I should have said 1/4 pi and a bit.

Because it's Microsoft. I bet they were originally planning on introducing Microsoft Calculus sometime. The calculator as is was just meant as a teaser for buying that.

[MdaG]

A. J. Raffles, on Nov 14 2005, 11:29 PM, said:

*makes another random guess* 0.838

You make me proud Raffles

[Qbix]

*duh*

What was *I* thinking ?

Well done AJ

[MdaG]

How about this one:

A company buys tires from two suppliers, 1 and 2. Supplier 1 has a record of delivering tires containing 10% defectives, whereas supplier 2 has a defective rate of only 5%. Suppose 40% of the current supply came from supplier 1. If a tire is taken from this supply and observed to be defective, find the probability that it came from supplier 1.

[BeefontheBone]

What we're looking for is the probability that a defective tyre in the supply was from supplier 1. Since 10% of theirs are defective and 40% of the supply is from them, 4% of the supply is both defective and from supplier 1 (or rather, the chance of both these occuring is 4%). Of the other 60% of the supply from supplier 2, 5% will be defective, so 3% of the total supply is defective and from supplier 2. Hence 7% of the total supply is defective (or rather, the chance of a random tyre being defective is 7%), and the chance of a defective tyre being from supplier 1 is 4/7, just over 57%.

The bigger question, of course, is why they continue to buy them from supplier 1 if 1 in 10 tyres is defective, unless they're extremely cheap, and their customers don't live long enough to tell anyone else about the shoddiness

[MdaG]

BeefontheBone, on Nov 15 2005, 04:37 PM, said:

What we're looking for is the probability that a defective tire in the supply was from supplier 1. Since 10% of theirs are defective and 40% of the supply is from them, 4% of the supply is both defective and from supplier 1 (or rather, the chance of both these occuring is 4%). Of the other 60% of the supply from supplier 2, 5% will be defective, so 3% of the total supply is defective and from supplier 2. Hence 7% of the total supply is defective (or rather, the chance of a random tire being defective is 7%), and the chance of a defective tire being from supplier 1 is 4/7, just over 57%.

Yup, yup, yup. Correct

[DannyMc252]

Its all supplier 1's fault.
Lets all blame supplier 1 for everything that's defective.

[MdaG]

DannyMc252, on Nov 16 2005, 12:45 AM, said:

Its all supplier 1's fault.
Lets all blame supplier 1 for everything that's defective.

Yeah, supplier 1 is a dildo!

[A. J. Raffles]

MdaG, on Nov 16 2005, 06:57 AM, said:

DannyMc252, on Nov 16 2005, 12:45 AM, said:

Its all supplier 1's fault.
Lets all blame supplier 1 for everything that's defective.

Yeah, supplier 1 is a dildo!

In that case it's rather surprising that he's capable of providing any tyres at all...