Question

18) A study is being conducted to estimate the traffic between two destinations. In sample of 12 cars, the average time spent was x ¯ = 48.2 minutes with a population standard deviation of σ =2.0 days. What is the margin of error for a 95% confidence interval for μ, the true average time spent in the hospital for this population? Round your answer to 3 decimal places.

Answer 1

Solution :

Given that,

Point estimate = sample mean =     = 48.2

Population standard deviation =    = 2

Sample size n =12

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z_/2 = Z_0.025 = 1.96   ( Using z table )

Margin of error = E =   Z_/2    * ( /n)
= 1.96 * ( 2 / 12)

= 1.132