Question

Actual lengths of pregnancy terms for a particular species of mammal are nearly normally distributed about a mean pregnancy length with a standard deviation of 18 days. About what percentage of births would be expected to occur more than 54 days after the mean pregnancy​ length?

Answer 1

Solution :

The data is normally distributed.

The standard deviation is 18 days

Here the data is normally distributed and 54 days is 3 days of standard deviation.

Therefore, the percentage of the births that would be $\text{expected to occur}$ within the 54 days of the mean $\text{pregnancy}$ length is given by :

= P( -3 < Z < 3)

= 0.9544

= 95 %

Therefore, about 95% of the births would be $\text{expected to occur}$ within 54 days of the men $\text{pregnancy}$ length.