A field biologist is studying black bear cubs in Yellowstone National Park. With the help of park rangers, he tranquilizes 17 bear cubs and their mothers and weighs the cubs. He calculates the margin of error in estimating the true mean weight of bear cubs and gets 5.818 lbs, at 95% confidence. Which of the following would produce a smaller margin of error?

______Weighing the cubs without tranquilizing them ______Weighing more cubs ______Weighing fewer cubs ______Using a higher confidence level