Length (in days) of human pregnancies is a normal random variable (X) with mean 266, standard deviation 16.
(It would be useful to sketch this normal distribution yourself, marking its mean and the values that are 1, 2, and 3 standard deviations below and above the mean. Click to compare your figure to ours )
The probability is 0.95 that a pregnancy will last between and days.
The shortest 16% of pregnancies last less than days.
The probability of a pregnancy lasting longer than 314 days is .
There is a probability of 0.5 that a pregnancy will last longer than days.