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Continuous random variables questions

I need some help with the following 2 questions, sure they are quick to answer but I'm having some problems with the given results of my text book.



In 2(i), I know that I would need to reverse it by finding P(lZl<a) = 1-0.611 = 0.389.

Then find invNorm((1-0.389)/2) = -0.507, however the given answer is 0.509.

I solve 2(j) by the same way (excluding doing the reverse) but also did not get the answer given by the text book.



In 10, I really dont know what to do when they put lX -300l < a.

Thank you very much in advance!
Samsoonie

....


For 2 i and j.

You've done this part correctly (below)
"In 2(i), I know that I would need to reverse it by finding P(lZl<a) = 1-0.611 = 0.389. "

Then:

P(|Z|<a)
= P(-a<Z<a)
= P(Z<a)-P(Z<-a) <=======
= P(Z<a)-[1-P(Z<a)] (by the symmetry of Z)
=2P(Z<a)-1

and this equals 0.389.

So, rearranging P(Z<a)= (0.389+1)/2

and you should be able to finish it to find a.

Edit: Corrected at <=======
Reply 2
Avatar for Samsoonie
Samsoonie
OP
ghostwalker
For 2 i and j.

You've done this part correctly (below)
"In 2(i), I know that I would need to reverse it by finding P(lZl<a) = 1-0.611 = 0.389. "

Then:

P(|Z|<a)
= P(-a<Z<a)
= P(Z<a)-P(-a<Z)
= P(Z<a)-[1-P(Z<a)] (by the symmetry of Z)
=2P(Z<a)-1

and this equals 0.389.

So, rearranging P(Z<a)= (0.389+1)/2

and you should be able to finish it to find a.


I really appreciate your help! Many thanks!
Samsoonie
I really appreciate your help! Many thanks!



Welcome.

Note: I've made a small correction to my previous post.

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