A pilot study is run to investigate the feasibility of recruiting pregnant women into a study of risk factors for preterm labor. Women are invited to participate at their first clinical visit for prenatal care. The following represent the gestational ages in weeks of women who consented to participate in the study. Compute a 95% confidence interval for the mean gestational age of women enrolling in the study.
11, 14, 21, 22, 9, 10, 13, 18