Among those taking the Graduate Record Exam , 18 people are randomly selected. This group had a mean score of 550 and a population standard deviation...

Among those taking the Graduate Record Exam , 18 people are randomly selected. This group had a mean score of 550 and a population standard deviation of 140. What is the 95% confidence interval for the population mean for the GRE test. Identify the point estimate for the mean and the margin of error.