The lengths of human pregnancies are normally distributed with a mean of 268 days and a standard deviation of 15 days. What is the probability that a pregnancy lasts at least 300 days?
A)0.0179
B)0.4834
C)0.0166
D)0.9834

Question

Quizplus · Accepted Answer

To find the probability that a pregnancy lasts at least 300 days, we use the Z-score formula: Z = (X - μ) / σ, where X is the value (300 days), μ is the mean (268 days), and σ is the standard deviation (15 days). Plugging in the values, we get Z = (300 - 268) / 15 = 32 / 15 ≈ 2.13. Looking up 2.13 in a standard normal distribution table or using a calculator, we find the area to the right (since we're interested in "at least") is approximately 0.0166.

The Lengths of Human Pregnancies Are Normally Distributed with a Mean