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A smaple of 90 detergents from “ABC” company is examined and the average amount of a...

  1. A smaple of 90 detergents from “ABC” company is examined and the average amount of a certain chemical per pack is 5 milligrams. The company has released standard deviation of that chemical contamination in the product to be 0.74 milligram per pack. Construct the 90% confidence interval of the true chemical contamination in all detergents of that company.
Math   Statistics-And-Probability   
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Answer #1

Let be the true chemical contamination in all detergents of that company

n = 90 (sample size)

= 0.74 (population standard deviation )

= 5 (sample mean)

For 90% confidence interval the level of significance() = 0.1

Critical value = = = = +/- 1.645 (we gey this value from z table)

Lower confidence limit =

Upper confidence limit =

Answer: 90% confidence interval of is ( 4.872 , 5.128 )

[Note : unit of the confidence interval is also milligram per pack]

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