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A student studies the strength of cables, which has a known population standard deviation of 16...

A student studies the strength of cables, which has a known population standard deviation of 16 kg. The student wants to obtain a 97% confidence interval for the mean strength, but with a margin of error not exceeding +/- 5.

How many cables does the student need to sample?

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Given A student studies the strength of cables, which has a known population standard deviation of = 16 kg. The student wants to obtain a 97% confidence interval for the mean strength, but with a margin of error not exceeding E = +/- 5, hence the minimum sample required is calculated as:

Where = (1-0.97)/2 = 0.015 and is calculated using the excel formula for normal distribution which is =NORM.S.INV(1-0.015), thus is computed as 2.17009

Now the minimum sample is calculated as:

Hence the student need to sample a minimum of 42.

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