THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION:
A school bus driver records the time (in minutes)it takes to commute to school for six days.Those results are: 25,22,17,20,15,and 10.Assuming the population is normally distributed,develop a 90% confidence interval for the population mean.
-Determine the reliability factor from the Student's t distribution table.
A)1.476
B)2.015
C)3.365
D)4.032

Question

Quizplus · Accepted Answer

A 90% confidence interval requires a reliability factor of 1.645 (for sample sizes less than 30) or 1.645 (for sample sizes greater than or equal to 30 and when the population standard deviation is unknown). However, since we do not know the population standard deviation, we must use a t-distribution. For a one-tailed test with 5 degrees of freedom (n-1), the reliability factor is 1.833. For a two-tailed test with 5 degrees of freedom, the reliability factor is 2.015. Since we are using a two-tailed test, the correct answer is B)2.015.