Question

The length of a pregnancy from conception to birth is approximately normally distributed with mean µ = 272 days and standard deviation σ = 9 days. What proportion of pregnancies last between 255 days and 300 days? Round your answer to 4 decimal places.

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Answer 1

We are given that the data follows the normal distribution with mean = 272 days and standard deviation = 9 days.

Let the last pregnancy be "X".

We have to find

We have to standardize the data value using

This can be written as:

Using the standard normal table we get:

Now, for

we know that the total area under the curve is 1,

So,

using the standard normal table we get:

Thus,

NOTE: The results may differ slightly due to decimal roundings.

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