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The length of human pregnancies from conception to birth varies
The length of human pregnancies from conception to birth varies according to a distribution that is approximately normal with mean 266 days and standard deviation 16 days.
a) What percent of pregnancies last less than 240 days (about 8 months)?
b) What percent of pregnancies last between 240 and 270 days (roughly between 8 and 9 months)
c) How long do the longest 20 % of pregnancies last?
Solution: (a) Here we need to compute
which means that 5.2081% of pregnancies last less than 240 days.
(b) Now we need
This implies that 54.6625% of pregnancies last between 240 and 270 days.
(c) We need to find C such that
This means that the longest 20 % of pregnancies last 279.4659 or more.
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