About _____ % of adults in the United States categorize themselves as infrequent drinkers

Why are t statistics more variable than z-scores?

a. The extra variability is caused by variations in the sample mean. b. The extra variability is caused by variations in the sample variance. c. The extra variability is caused by variations in the df value. d. None of the other options explains the extra variability for t statistics.

According to the ethical principle of informed consent, when should participants be told about the procedures involved in a study?

A. at least 7 days before the start of the study B. immediately before the start of the study C. once they start to experience distress while in the study D. immediately after the study has ended