Answer:
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.
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Let's solve your equation step-by-step.<span><span><span>−18</span>−<span>6k</span></span>=<span>6<span>(<span>1+<span>3k</span></span>)
</span></span></span>Step 1: Simplify both sides of the equation.
<span><span><span>−18</span>−<span>6k</span></span>=<span>6<span>(<span>1+<span>3k</span></span>)
</span></span></span><span>Simplify: (Show steps)</span><span><span><span>−<span>6k</span></span>−18</span>=<span><span>18k</span>+6
</span></span>Step 2: Subtract 18k from both sides.<span><span><span><span>−<span>6k</span></span>−18</span>−<span>18k</span></span>=<span><span><span>18k</span>+6</span>−<span>18k</span></span></span><span><span><span>−<span>24k</span></span>−18</span>=6
</span>Step 3: Add 18 to both sides.<span><span><span><span>−<span>24k</span></span>−18</span>+18</span>=<span>6+18</span></span><span><span>−<span>24k</span></span>=24
</span>Step 4: Divide both sides by -24.<span><span><span>−<span>24k</span></span><span>−24</span></span>=<span>24<span>−24</span></span></span><span>k=<span>−1
</span></span>Answer:<span>k=<span>−<span>1</span></span></span>