STUCK AGAIN ... one more question ... sorry!

[bec036]

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! 

[thedpinsane]

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  

[bec036]

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

[thedpinsane]

No problem 

[mikee65]

One of those questions is really tricky only 2% got full marks I think, subtle conditional probability aha

[bec036]

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.

[werdna]

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.

[bec036]

haha okay!

ANI thank you

[thedpinsane]

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

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

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

Ps - Methods today = FAIL 

[werdna]

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.

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.