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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: bec036 on November 07, 2010, 08:49:12 am

Title: STUCK AGAIN ... one more question ... sorry!
Post by: bec036 on November 07, 2010, 08:49:12 am
2009 VCAA:
Question 3d.
These answers are better than VCAA in terms of working ....
http://www.itute.com/wp-content/uploads/2009-vcaa-mathematical-methods-cas-exam-2-solutions-v2.pdf

Both VCAA and this say Pr(X<68.4) = 0.995 and I have no clue how to get that! I can get 0.99 which was a "commonly used incorrect value" but 0.995 throws me!

I bet its really simple and I just cant see it!  :'(
Title: Re: STUCK AGAIN ... one more question ... sorry!
Post by: thedpinsane on November 07, 2010, 09:30:38 am
The question states that:-

'BBC management wants engineers to change the manufacturing process so that 99% of all balls produced have diameter between 65.6 and 68.4 mm.'

Therefore Pr(65.6<X<68.4)=0.99

If you draw the normal dist. graph and the points 65.6 and 68.4, 99% of the probability will be between those points and 1% will be outside those points.

Therefore Pr(X<65.6)=0.005 and Pr(X>68.4)=0.005 (Forgot the extra 0's)

Then you'll understand that Pr(X<68.4)=0.995

Hope this helps  :)
Title: Re: STUCK AGAIN ... one more question ... sorry!
Post by: bec036 on November 07, 2010, 09:32:45 am
Oo that makes sense I knew it had something to do with the graph but couldn't work it out! Thank you so much! it seems so simple now :)
Title: Re: STUCK AGAIN ... one more question ... sorry!
Post by: thedpinsane on November 07, 2010, 09:34:43 am
No problem  :)
Title: Re: STUCK AGAIN ... one more question ... sorry!
Post by: mikee65 on November 07, 2010, 09:46:02 am
One of those questions is really tricky only 2% got full marks I think, subtle conditional probability aha
Title: Re: STUCK AGAIN ... one more question ... sorry!
Post by: bec036 on November 07, 2010, 09:57:27 am
One of those questions is really tricky only 2% got full marks I think, subtle conditional probability aha
Was that 3ci? Cause if it was yay! On of the ones i got right haha.
Title: Re: STUCK AGAIN ... one more question ... sorry!
Post by: werdna on November 08, 2010, 09:57:31 am
The question states that:-

'BBC management wants engineers to change the manufacturing process so that 99% of all balls produced have diameter between 65.6 and 68.4 mm.'

Therefore Pr(65.6<X<68.4)=0.99

If you draw the normal dist. graph and the points 65.6 and 68.4, 99% of the probability will be between those points and 1% will be outside those points.

Therefore Pr(X<65.6)=0.005 and Pr(X>68.4)=0.005 (Forgot the extra 0's)

Then you'll understand that Pr(X<68.4)=0.995

Hope this helps  :)

ANI YOU GENIUS!!!! ANI YOU GENIUS!!!

This guy likes to be called Ani, so when you get to thank him, call him Ani. :D
Title: Re: STUCK AGAIN ... one more question ... sorry!
Post by: bec036 on November 08, 2010, 10:12:19 am
haha okay!

ANI thank you :)

Title: Re: STUCK AGAIN ... one more question ... sorry!
Post by: thedpinsane on November 08, 2010, 03:09:02 pm

ANI YOU GENIUS!!!! ANI YOU GENIUS!!!

This guy likes to be called Ani, so when you get to thank him, call him Ani. :D

Andrew, I don't think I  hit you hard enough with that ruler this morning.  :uglystupid2:

Ps - Methods today = FAIL  :'(
Title: Re: STUCK AGAIN ... one more question ... sorry!
Post by: werdna on November 08, 2010, 04:07:56 pm
haha okay!

ANI thank you :)



Good work! :)

ANI YOU GENIUS!!!! ANI YOU GENIUS!!!

This guy likes to be called Ani, so when you get to thank him, call him Ani. :D

Andrew, I don't think I  hit you hard enough with that ruler this morning.  :uglystupid2:

Ps - Methods today = FAIL  :'(

DUDE... MY methods was faillllll.