Acivil engineer is analyzing the compressive strength of concrete. compressive strength is normally distributed with σ = 31.62 psi. a random sample of 36 specimens has a mean compressive strength of 3250 psi. suppose we wish to create a 99% confidence interval with a maximum width of 3 psi. what sample size is required?

A sample size of at least 737 specimens is required.

Step-by-step explanation:

We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of .

So it is z with a pvalue of , so

Now, find the width M as such

In which is the standard deviation of the population and n is the size of the sample.

In this problem, we have that:

So:

A sample size of at least 737 specimens is required.

if your equation is in the form ax2 + bx + c, you can find the maximum by using the equation:

max = c - (b2 / 4a).

the first step is to determine whether your equation gives a maximum or minimum.

-x2 + 4x - 2.     thats an example hope it