A company wants to estimate the time its trucks take to drive from city A to city B.The standard deviation is known to be 12 minutes.What sample size is required so that the error does not exceed ±2 minutes,with 95 percent confidence?
A)12 observations
B)139 observations
C)36 observations
D)129 observations

Question

Quizplus · Accepted Answer

The sample size required for a confidence interval with a margin of error of ±2 minutes and a confidence level of 95% is given by:n = (Z^2 * s^2) / e^2where:Z is the z-score for the desired confidence level (95% = 1.96)s is the standard deviation (12 minutes)e is the margin of error (2 minutes)Plugging in the values, we get:n = (1.96^2 * 12^2) / 2^2 = 138.24Rounding up to the nearest whole number, we get a sample size of 139 observations.

A Company Wants to Estimate the Time Its Trucks Take