The lengths of nails produced in a factory are normally distributed with a mean of 3.34 centimeters and a standard deviation of 0.07 centimeters. Find the two lengths that separate the top 3% and the bottom 3%. These lengths could serve as limits used to identify which nails should be rejected. Round your answer to the nearest hundredth, if necessary.

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andromache andromache · Answer 1 · 2020-07-23T05:10:58+02:00

Answer:

3.47 and 3.21

Step-by-step explanation:

Let us assume the nails length be X

[tex]X \sim N(3.34,0.07^2)[/tex]

Value let separated the top 3% is T and for bottom it would be B

[tex]P(X < T)= 0.97[/tex]

Now converting, we get

[tex]P(Z < \frac{T-3.34}{0.07})= 0.97[/tex]

Based on the normal standard tables, we get

[tex]P(Z < 1.881)= 0.97[/tex]

Now compare these two above equations

[tex]\frac{T-3.34}{0.07} = 1.881 \\\\ T = 1.881 \times 0.07 + 3.34 \\\\ = 3.47[/tex]

So for top 3% it is 3.47

Now for bottom we applied the same method as shown above

[tex]P(Z < \frac{B-3.34}{0.07})= 0.03[/tex]

Based on the normal standard tables, we get

[tex]P(Z < -1.881)= 0.03[/tex]

Now compare these two above equations

[tex]\frac{B-3.34}{0.07} = -1.881[/tex]

[tex]= -1.881 \times 0.07 + 3.34 \\\\ = 3.21[/tex]

hence, for bottom it would be 3.21