Question

According to the World Health Organization (WHO) Child Growth Standards, the head circumference for boys at birth has a normal probability distribution with a mean of 34.5cm and a standard deviation of 1.3 cm.

What is the head circumference of a newborn boy who marks the start of the 75th percentile? Enter a number without units

I need help answering this static problem

Answer 1

Solution: It is given here:

u= 34.5, 0 = 1.3

We are required to find the head circumference of a newborn boy who marks the start of the 75th percentile.

To find the 75th percentile value, we have to first find the z-value corresponding to area = 0.75. Using the standard normal table, we have:

(0.75) = 0.6745

Now using the z-score formula, the 75th percentile value is:

P75 — и

0.6745 - P5 — 34.5 1.3

0.6745 x 1.3 = P75 - 34.5

0.87685 = P75 – 34.5

P-5 = 34.5 +0.87685

P75 = 35.38

Therefore, the head circumference of a newborn boy who marks the start of the 75th percentile is 35.38