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

User Lavina
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1 Answer

4 votes

Answer:97 rods

Explanation:

The number of steel rods for 95% confidence level


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


Z_(\alpha )/(2)=1.96

E=3


\hat{\sigma }=15

Substituting values


n=\left ( (1.96* 15)/(3)\right )^2


n=96.04\approx 97

Thus 97 rods is tested

User Kaspars Ozols
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