An SRS of 20 recent birth records at the local hospital were selected. In the sample, the average birth weight was 121.4 ounces and the standard deviation (SD+) was 7.5 ounces. Assume that in the population of all babies born in this hospital, the birth weights follow a Normal distribution, with some mean (Average of box). We are interested in a 95% confidence interval for the population mean birth weight. The margin of error associated with the confidence interval is