The lengths of a particular animal's pregnancies are approximately normally distributed, with mean muequals252 days and standard deviation sigmaequals12 days.
(a) What proportion of pregnancies lasts more than 273 days?
(b) What proportion of pregnancies lasts between 249 and 261 days?
(c) What is the probability that a randomly selected pregnancy lasts no more than 237 days?
(d) A "very preterm" baby is one whose gestation period is less than 234 days. Are very preterm babies unusual?
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Laureneon Laureneon · Answer 1 · 2024-06-29T21:48:34-04:00

Step-by-step explanation:

Normalcdf on a TI-84 is found by pressing 2nd->vars->2

A) normalcdf(low = 273, high = ∞, mu = 252, sd = 12) = .04

B) normalcdf(low = 249, high = 261, mu = 252, sd = 12) = .372

C) normalcdf(low = 0, high = 237, mu = 252, sd = 12) = .106

D) normalcdf(low = 0, high = 234, mu = 252, sd = 12) = .067

Yes, this is unusual since there is only a 6.7% chance of it occurring.

Hope this helps!

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