The lengths of pregnancies in a small rural village are norm

The lengths of pregnancies in a small rural village are normally distributed with a mean of 263 days and a standard deviation of 17 days. A distribution of values is normal with a mean of 263 and a standard deviation of 17.

What percentage of pregnancies last beyond 227 days?
P(X > 227 days) =  %

Enter your answer as a percent accurate to 1 decimal place (do not enter the \"%\" sign). Answers obtained using exact z-scores or z-scores rounded to 3 decimal places are accepted.

Solution

Normal Distribution
Mean ( u ) =263
Standard Deviation ( sd )=17
Normal Distribution = Z= X- u / sd ~ N(0,1)                  
P(X > 227) = (227-263)/17
= -36/17 = -2.1176
= P ( Z >-2.118) From Standard Normal Table
= 0.9829                  
= 98.29% are beyond 227