Question

The length of human pregnancies from conception to birth varies according to a distribution that is approximately Normal with a mean of 266 days and a standard deviation of 16 days. Between what two values do the middle 95% of the lengths of all pregnancies fall?

a.Between 218 and 314 days
b.Between 234 and 298 days
c.Between 202 and 330 days
d.Between 250 and 282 days

Answer 1

[ 250 , 282 ]

Explanation:

A Normal Distribution N ( 0,1)

We know one of the characteristics of a normal distribution is the symmetry and the fact that in the interval of

μ₀ - σ and μ₀ + σ are found the 95.5 % of all values

In our case we have μ₀ = 266 and the standard deviation σ = 16

So μ₀ - σ ⇒ 266 - 16 = 250 the lowest value for the interval and

μ₀ + σ ⇒ 266 + 16 = 282 the highest value for the interval

The interval with 95.5 % of all values is

[ 250 , 282 ]