So, for each research hypothesis which is also referred to as the alternative hypothesis , there is a complementary null hypothesis. They are inseparable. It's like two sides of a coin. Listed below are examples of directional, nondirectional, and null hypotheses for difference or relationship statements. There is a difference in average teacher salaries between small and large districts.
Large districts have higher average teacher salaries than small districts.
There is no difference in average teacher salaries between large and small districts. There is a relationship between size of district and average teacher salary. There is a positive relationship between size of district and average teacher salary. OR Larger districts have higher average teacher salaries than smaller districts. There is no relationship between size of district and average teacher salary.