Engineers must consider the breadths of male heads when designing helmets. The company researchers have determined that the population of potential clientele have head breadths that are normally distributed with a mean of 6.5-in and a standard deviation of 1-in. Due to financial constraints, the helmets will be designed to fit all men except those with head breadths that are in the smallest 1.9% or largest 1.9%. a) What is the minimum head breadth that will fit the clientele? b) What is the maximum head breadth that will fit the clientele?

a) min = 4.4251

b) max = 8.5743

Step-by-step explanation:

Given:

Mean, u = 6.5

Standard deviation = 1

To get our values, we are to use the inverse of the standard normal table.

a) The minimum head breadth that will fit.

P(Z < z) = 1.9%

P(Z < z) = 0.019

P(Z < -2.0749) = 0.019

z = -2.0749

From the z-score formula, we have:

Let x be the breath of heads.

Making x the subject of the formula, we have:

We already have:

z = -2.0749

u = 6.5

s.d = 1

Substituting figures, we have:

x = (-2.0749 * 1) + 6.5

x = 4.4251

The minimum head breadth that will fit the clientele is 4.4251

b) The maximum head breadth that will fit.

P(Z > z) = 1.9%

1 - P(Z < z) = 0.019

P(Z < z) = 1 - 0.019 = 0.981

P(Z < 2.0749) = 0.981

From the z-score formula, we have:

Let x be the breath of heads.

Making x the subject of the formula, we have:

We already have:

z = 2.0749

u = 6.5

s.d = 1

Substituting figures, we have:

x = (2.0749 * 1) + 6.5

x = 4.4251

x = 8.5743

The maximum head breadth that will fit the clientele is 8.5743