• Pick one statistical concept and describe its application in the article. Be specific.
• Discuss the importance of this statistical concept to the study described in the article.

Handy experiment

Initially, Honor compared the hands of her newborn niece and cousins to the rock art. A simple comparison showed that the ancient prints were too small to be human, but she needed a larger sample of hands to say for sure. [Photos: 'Winged Monster' Rock Art in Black Dragon Canyon]

So Honor worked with the Lille University Hospital in northern France, and ended up getting the hand measurements of 25 preterm babies and 36 typical babies who survived birth. "We were really surprised; all of the parents agreed to [let their babies] take part in the experiment," Honor said. "They were very enthusiastic that their babies could contribute to a scientific study."

Honor and her colleagues also measured 11 of the tiny hands at the Wadi Sura II site. (The other two were incomplete and difficult to measure, she said.) In addition, they measured 30 of the large hands at Wadi Sura II and 30 hands from living adults, and found that they matched well, she said.

But several parameters indicated that the tiny hands were not human. Though the stenciled fingers were long, overall the hands were small just 1.8 inches (4.5 centimeters) from the base of the palm to the end of the middle finger. That's much smaller than a human baby hand, which measures an average of 2.4 inches (6.2 cm) long, she said "We were completely shocked by our own research because it brought up the question if it's not babies, what is it?" Honor said.