Question

Engineers want to design seats in commercial aircraft so that they are wide enough to fit 90% of all males. (Accommodating 100% of males would require very wide seats that would be much too expensive.) Men have hip breadths that are normally distributed with a mean of 14.2 in. and a standard deviation of 1.1 in. Find P90. 

That is, find the hip breadth for men that separates the smallest 90% from the largest 10%. 

The hip breadth for men that separates the smallest 90% from the largest 10% is P90 = _______ in. (Round to one decimal place as needed.)

Answer 1

Given that, mean (μ) = 14.2 inches and

standard deviation = 1.1 inches

We want to find, P90. That means, we want to find, the value of x such that, P(X < x) = 0.90

Therefore, the hip breadth for men that separates the smallest 90% from the largest 10% is P90 = 15.6 in.