If the mean of breaking strength of a copper wire is 575 pounds with a standard deviation of 8.3 pounds how large a sample must be used in order that there be one chance in 100 that the mean breaking strength of the sample is less than 572 pounds?
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Expert's answer
2020-12-21T17:02:45-0500
z=(x-mean)/σ/n=(572−575)/8.3/n or |z|=3n/8.3
we need to find that value of x for which
0.01=area to the right at the variate z
that is area to the left=1-0.01=0.99=0.5+0.49
From the areas under the standard normal curve the corresponding value of z is 2.33. Hence
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