The lengths of a particular animal's pregnancies are approximately normally distributed, with μ=261and standard deviation= 88.
What proportion of pregnancies lasts between 251 and 267 days?
What is the probability that a randomly selected pregnancy lasts no more than 245 days?
A "very preterm" baby is one whose gestation period is less than 243 days. Are very preterm babies unusual?
Solution :
Given that ,
mean = = 261
standard deviation = = 88
P(251< x < 267) = P[(251-261) /88 < (x - ) / < (267-261) / 88)]
= P( -0.11< Z < 0.07)
= P(Z <0.07 ) - P(Z <-0.11 )
Using z table
= 0.5279-0.4562
proportion= 0.0717
(B)
P(X< 245) = P[(X- ) / < ( 245-261) /88 ]
= P(z <-0.18 )
Using z table
= 0.4286
probability=0.4286
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