Question: Biologists at the Long Beach aquarium would like to know if conditions at aquariums reduce the life span of dolphins. Dolphins live an average of 21 years in the wild with a standard deviation of 3 years. Furthermore, the lifespan of dolphins forms a normal distribution.

Because dolphins are exchanged with other aquariums and because some dolphins’ ages are unknown, the biologists were able to randomly select only 4 dolphins for the study. The four lived to the following ages: 17, 19, 20, 21. At a .05 significance level, can the biologists claim that dolphins living in captivity have a shorter life span than dolphins at sea?