anonymous one year ago Medal and Fan will be given!! The length of human pregnancies varies according to an approximately normal distribution with a mean of 266 days and variance of 256 days. How long are the longest 2.5% of all pregnancies? (Explanation question. No multiple Choice) Please help!

1. anonymous

@pooja195 @dan815 @ganeshie8 @Hero @Kainui @kiamousekia @Howard-Wolowitz

2. anonymous

3. anonymous

@Abhisar Can you please help. This is my last question.

4. anonymous

need help please @Michele_Laino

5. Michele_Laino

here we have to refer to the "erf" function

6. anonymous

Okay. That is what I am confused on... @Michele_Laino

7. Michele_Laino

the standard deviation, of your distribution, is: $\Large \sigma = \sqrt {256} = 16$

8. anonymous

Okay. I got it so far @Michele_Laino

9. anonymous

So now what? @Michele_Laino

10. Michele_Laino

please wait, I'm working on your question...

11. anonymous

Oh yeah sure. Take your time :D @Michele_Laino

12. Michele_Laino

I think that your problem requests for this value: |dw:1441213069159:dw|

13. Michele_Laino

from the table of the "erf" function we get: $\large N = 266 + 1.96 \cdot \sigma = 266 + 1.96 \cdot 16 = 297.36 \cong 297$

14. anonymous

Okay so is that our final answer though? 297? @Michele_Laino

15. Michele_Laino

yes! I think so!

16. anonymous

Oh my god! Thank you so much! That was very hard but you made it so easy! Thank you! Fan and medal! :) @Michele_Laino

17. Michele_Laino

:)

18. Michele_Laino

please wait I have a doubt: maybe the requested reasoning can be this: |dw:1441214281328:dw| so we have: $\Large 266 + 2.24 \cdot 16 = 301.84 \cong 302$