Reliable scientific conclusions are based on verifiable empirical evidence. But data must be transformed and interpreted before they become evidence, and statistical inference plays an important role in the process of interpretation. Biologists use statistics to organize and analyze data so that they can make inferences and use the data as evidence. Students should have opportunities to collect and analyze data in their biology classes as well. In this activity, students collect data on the surface areas of sun leaves and shade leaves, then analyze the data using the independent-samples t-test. The t-test procedure can be used in investigations where two groups are compared on one dependent variable.