Answer true or false to each statement concerning a confidence interval for a population mean. Give reasons for your answers.
a. The length of a confidence interval can be determined if you know only the margin of error.
b. The margin of error can be determined if you know only the length of the confidence interval.
c. The confidence interval can be obtained if you know only the margin of error.
d. The confidence interval can be obtained if you know only the margin of error and the sample mean.