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hodyreva [135]
4 years ago
8

A scientist wishes to estimate the mean breaking strength of a certain type of steel rod within 3.0 psi with 95% confidence. Bas

ed on experience with a similar type of steel, she believes the standard deviation is approximately 15.0 psi in individual breaking strengths. How many steel rods should she test?
Mathematics
1 answer:
yaroslaw [1]4 years ago
6 0

Answer:97 rods

Step-by-step explanation:

The number of steel rods for 95% confidence level

n=\left ( \frac{Z_\frac{\alpha }{2}\times \hat{\sigma }}{E} \right )^2

Z_\frac{\alpha }{2}=1.96

E=3

\hat{\sigma }=15

Substituting values

n=\left ( \frac{1.96\times 15}{3}\right )^2

n=96.04\approx 97

Thus 97 rods is tested

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Hank has to drain his pool so repairs can be done on a crack on the bottom. The company coming to fix the pool is scheduled to a
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The answer to the question: "Will Hank have the pool drained in time?" is:

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Step-by-step explanation:

To identify the time Hank needs to drain the pool, we can begin with the time Hank has from 8:00 AM to 2:00 PM in minutes:

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Now, we use a rule of three:

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And we calculate:

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As we know, <u><em>Hank has 360 minutes to drain the pool and how it would be drained in 326 minutes approximately, we know Hank will have the pool drained in time and will have and additional 34 minutes</em></u>.

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