mariomintchev 2 years ago Help with #6 on the worksheet....

1. mariomintchev

2. mariomintchev

this is what i have: |dw:1360104752412:dw|

3. mariomintchev

b) Expected Value (Height) = ? c) Pr(X>160) d) e) Pr(165<x<185) f) Pr(X>185) Help????

4. mariomintchev

@robtobey @phi

5. mariomintchev

ok b) is 1/(b-a) so 1/(210-150)

6. mariomintchev

hi @Jemurray3 ! :D

7. mariomintchev

**** c) Pr(X<160)

8. Jemurray3

What you said above, 1/(b-a), is the probability density function: P(x) = 1/(b-a) for all x between a and b, and zero elsewhere. Because it's constant, you can multiply it by the length of any interval to find the probability that someone's height falls in said interval. So, (c) is (160-150) / (210-150) = 10/60 = 1/6.

9. mariomintchev

o ok i see... please continue.... my notes have what you just said but are not very clear....

10. mariomintchev

for D would it be 2 times the numerator??

11. Jemurray3

The expectation value is fairly clearly the average height. The rest are just multiplying your probability density function by intervals of different lengths.

12. Jemurray3

No, it is not. If A and B are uncorrelated random events, then P(A and B) = P(A) * P(B)

13. mariomintchev

so 1/6 times 1/6 ??

14. Jemurray3

Yes

15. mariomintchev

sweeeeet

16. mariomintchev

for part E would i do: (185-165)/(210-150) ??

17. Jemurray3

yes

18. mariomintchev

and F would be (210-200)/(210-150) ?? lol

19. mariomintchev

@Jemurray3 , you still alive? haha

20. Jemurray3

You seem to understand it well enough without me at this point

21. mariomintchev

ok. im just making sure.