I need help with the (b) portion of the question... mathxl.com/student/PlayerHom

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I need help with the (b) portion of the question...

mathxl.com/student/PlayerHomework.aspx?homeworkld-354508270&questionld-11;&flushed-false;&cld; anita orzel rk: 2-2 MyStatl.ab: Module Two Problem Set 14 8.1.19 Ex. Score: 0 of 5 pts Hw Score: 63.85% (41.5 of 65 pts) 10 of 14 complete Suppose the lengths of the pregnancies of a certain animal are approximately normally dis of the pregnancies of a certain animal are approximately normally distributed with mean 123 days and standard deviation 11 days. (a) What is the probablity that a randomly selected pregnancy lasts less The probability that a randomly selected pregnancy lasts less than 119 days is approximately o that a randomly selected pregnancy lasts less than 119 days? decimal places as needed) 3594. Round to four Te (b) Wha t is the probability that a random sample of 15 pregnancies has a mean gestation period of 119 days or less? that the mean of a a random sample of 15 pregnancies is less than 119 days is approximately(Round to four decimal places as needed.) pri

Explanation / Answer

b.

Mean ( u ) =123
Standard Deviation ( sd )=11
Number ( n ) = 15
Normal Distribution = Z= X- u / (sd/Sqrt(n) ~ N(0,1)                  
P(X > 119) = (119-123)/11/ Sqrt ( 15 )
= -4/2.84= -1.4084
= P ( Z >-1.4084) From Standard Normal Table
= 0.9205                  
P(X < = 119) = (1 - P(X > 119)
= 1 - 0.9205 = 0.0795                  

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