Ostriches live in hot environments, and they are normally exposed to the sun for long periods. Some animals have special mechanisms for reducing the temperature of their brain relative to their body temperature. A researcher wanted to construct a confidence interval to study the difference between an ostrich's body temperature and brain temperature during some typical hot weather. What confidence interval would she use? One mean, sigma known. One mean, sigma unknown. Mean of differences, using dependent samples (paired data). Difference of two means, using independent samples