Delivery time by courier services is important to stock brokers.One such firm wishes to estimate the average time taken by couriers delivering negotiable securities in New York City.Specifically,the firm randomly samples 36 courier pickup and delivery times.The collected data,in minutes,represent the time between pickup and delivery.Suppose the population standard deviation is 0.3 minutes and the sample mean is 9.975.Find the sample mean and compute.A 90-percent confidence interval for the true mean delivery time, $\mu$ is:
A) 9.852 to 10.05.
B) 119.60 to 119.80.
C) 119.62 to 119.78.
D) 119.26 to 119.87.
E) 9.893 to 10.057.

Question

Quizplus · Accepted Answer

The 90% confidence interval for the mean is calculated using the formula: $\bar{x} \pm z \times \frac{\sigma}{\sqrt{n}}$. Here, $\bar{x} = 9.975$, $\sigma = 0.3$, $n = 36$, and $z$ for 90% confidence is approximately 1.645. The interval is 9.975 ± 1.645 * (0.3/6), which results in 9.893 to 10.057.

Delivery Time by Courier Services Is Important to Stock Brokers μ\muμ

Delivery Time by Courier Services Is Important to Stock Brokers $\mu$