Question

The diameters of bolts produced in a machine shop are normally distributed with a mean of 5.71 millimeters and a standard deviation of 0.08 millimeters. Find the two diameters that separate the top 4% and the bottom 4%. These diameters could serve as limits used to identify which bolts should be rejected

Answer 1

Answer:

The bolts with diameter less than 5.57 millimeters and with diameter greater than 5.85 millimeters should be rejected.

Step-by-step explanation:

We have been given that the diameters of bolts produced in a machine shop are normally distributed with a mean of 5.71 millimeters and a standard deviation of 0.08 millimeters.    

Let us find the sample score that corresponds to z-score of bottom 4%.  

From normal distribution table we got z-score corresponding to bottom 4% is -1.75 and z-score corresponding to top 4% or data above 96% is 1.75.

Upon substituting these values in z-score formula we will get our sample scores (x) as:

$z=\frac{x-\mu}{\sigma}$

$-1.75=\frac{x-5.71}{0.08}$

$-1.75*0.08=x-5.71$

$-0.14=x-5.71$

$-0.14+5.71=x-5.71+5.71$

$5.57=x$

Therefore, the bolts with diameters less than 5.57 millimeters should be rejected.

Now let us find sample score corresponding to z-score of 1.75 as upper limit.

$1.75=\frac{x-5.71}{0.08}$

$1.75*0.08=x-5.71$

$0.14=x-5.71$

$0.14+5.71=x-5.71+5.71$

$5.85=x$  

Therefore, the bolts with diameters greater than 5.85 millimeters should be rejected.