What are the appropriate H0 and Ha for each of the following research studies? In addition, note whether the hypothesis test is one- or two-tailed.
a. A study in which researchers want to test whether there is a difference in spatial ability between left- and right-handed people.
b. A study in which researchers want to test whether nurses who work 8-hour shifts deliver higher-quality work than those who work 12-hour shifts.
c. A study in which researchers want to determine whether crate-training puppies is superior to training without a crate.