A highway inspector needs an estimate of the mean weight of trucks crossing a bridge on the interstate highway system. She selects a random sample of 49 trucks and finds a mean of 15.8 tons with a sample standard deviation of 3.85 tons. The 90 percent confidence interval for the population mean is:
A)14.72 to 16.88 tons.
B)14.90 to 16.70 tons.
C)14.69 to 16.91 tons.
D)14.88 to 16.72 tons.

Question

Quizplus · Accepted Answer

The 90% confidence interval is calculated using the formula: mean ± (z * (standard deviation/√n)). For a 90% confidence level, the z-value is approximately 1.645. Plugging in the values: 15.8 ± (1.645 * (3.85/√49)) gives the interval 14.88 to 16.72 tons.

A Highway Inspector Needs an Estimate of the Mean Weight