A manufacturer of ovens tests 10 ovens by cooking in each a 20 pound turkey. The turkeys are placed in 325 degrees Fahrenheit oven until a thermometer probe indicates that the turkey is “done” (when internal temperature reaches 165 degrees). The amount of time this takes is recorded for each oven. A 95% confidence interval for the time it takes is (246 ; 310) minutes. Which of the following would result in a smaller (narrower) confidence interval?