Please explain how you got the answer. Thank you. The length of human pregnancie
ID: 3207047 • Letter: P
Question
Please explain how you got the answer.
Thank you.
The length of human pregnancies from conception to birth varies according to a distribution that is approximately Normal with mean 263 days and standard deviation 13 days. What proportion of pregnancies last less than 270 days (about 9 months)? (Please use 4 decimal places.) What proportion of pregnancies last between 240 and 270 days (roughly between 8 months and 9 months)? (Please use 4 decimal places.) How long do the longest 20% of pregnancies last? (Please use 2 decimal places.)Explanation / Answer
a) Z=(270-263)/13 = 0.54, so P(x<270) =0.7054 ( from normal distribution table)
b) Z for 240 , (240-263)/13 =-1.77 , P(240<X<270) =P(z<0.54)-(1-P(z<1.77))=0.7054-(1-0.9616)=0.667
c) we need to find the top most value at 80% , for 80% the value of z from normal distribution table is 0.84
(x-263)/13 =0.84
therefore x=0.84*13+263
=273.92