We intend to estimate the average driving time of a group of commuters. From a previous study, we believe that the average time is 42 minutes with a standard deviation of 12 minutes. We want our 98 percent confidence interval to have a margin of error of no more than plus or minus 3 minutes. What is the smallest sample size that we should consider?
A) 87
B) 10
C) 8
D) 261

Question

Quizplus · Accepted Answer

To find the smallest sample size, use the formula for margin of error: ME = Z * (σ/√n). For a 98% confidence interval, Z is approximately 2.33. Solving for n with ME = 3, σ = 12 gives n ≈ 87.

We Intend to Estimate the Average Driving Time of a Group