Researchers fed mice a specific amount of Aldrin, a poisonous pesticide, and studied their nervous systems to find out why Aldrin causes convulsions. The absolute refractory period, time required for nerves to recover after a stimulus, was measured and varies Normally. The measurements, in milliseconds, for five mice were 2.1, 2.3, 2.3, 2.4, and 2.5.

Part A: Find the mean refractory period and the standard error of the mean. (2 points)