The speeds of 80 vehicles were collected from a roadway section to estimate the mean speed....

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Civil Engineering

The speeds of 80 vehicles were collected from a roadway sectionto estimate the mean speed. The margin of error for this samplemean was reported as 4 km/h at the confidence level of 90%. What isthe sample size required to reduce this margin of error to 2 km/h(i.e., to ensure that the true mean is within ±2km/h of the samplemean 90% of the time)?

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The margin of error is given by the equationWhereE margin of errorz z score corresponding to the confidence interval population standard deviationn sample    See Answer
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