Question

ch 3* 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. about 95% of all pregnancies last between

234 and 298 days.
250 and 282 days.
218 and 314 days.

question 3
ch 3* to completely specify the shape of a normal distribution, you must give
the mean and the standard deviation.
the median and the quartiles.
the five - number summary.

Explanation:

Step1: Recall the empirical rule for normal distribution

For a normal - distributed data, about 95% of the data lies within 2 standard deviations of the mean.

Step2: Calculate the lower bound

The lower bound is $\mu - 2\sigma$, where $\mu = 266$ (mean) and $\sigma=16$ (standard deviation). So, $266-2\times16=266 - 32=234$.

Step3: Calculate the upper bound

The upper bound is $\mu + 2\sigma$. So, $266+2\times16=266 + 32=298$.
For the second question, a normal distribution is completely specified by its mean and standard - deviation.

Answer:

First question: 234 and 298 days.
Second question: the mean and the standard deviation.