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Mileage tests are conducted for a particular model of automobile. If a 99% confidence interval with...

Mileage tests are conducted for a particular model of automobile. If a 99% confidence interval with a margin of error of  mile per gallon is desired, how many automobiles should be used in the test? Assume that preliminary mileage tests indicate the standard deviation is 2.7 miles per gallon.

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Answer #1

Solution :

Given that,

standard deviation = = 2.7

margin of error = E = 1

At 99% confidence level the z is ,

  = 1 - 99% = 1 - 0.99 = 0.01

/ 2 = 0.01 / 2 = 0.005

Z/2 = Z0.005 = 2.576

Sample size = n = ((Z/2 * ) / E)2

= ((2.576 *2.7) / 1)2

= 48.3748

= 48

Sample size = 48

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