A medical researcher wants to estimate μ, the mean weight of babies born to women over the age of 40. The researcher chooses a random sample of 100 pregnant women who are over 40. Using the mean birth weight of the 100 babies in the sample, the researcher calculates the 95% confidence interval for μ. With 95% confidence, the researcher estimates the mean birth weight of all babies born to women who are over the age of 40 to be between 2935 and 3135 grams. The researcher wants to maintain the 95% level of confidence but report a confidence interval with a smaller margin of error. What should she do?