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Assume that the duration of all human pregnancies can be described by a Normal model with...

Assume that the duration of all human pregnancies can be described by a Normal model with mean 262 days and standard deviation 18 days. What percentage of all human pregnancies should last between 255 and 270 days? Give your answer to 4 decimal places.

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Answer #1

Solution :

Given that,

mean = = 262

standard deviation = = 18

P (255 < x < 270)

P ( 255 - 262 / 18) < ( x -  / ) < ( 270 - 262 / 18)

P ( - 7 / 18 < z < 8 / 18)

P (-0.87 < z < - 0.259)

P ( z < - 0.259 ) - P ( z < -0.87)

Using z table

= 0.6700- 0.1922

= 0.4778

Probability = 0.4778 = 47.78%

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