Final answer:
The degrees of freedom for a hypothesis test involving the difference between two population means with unknown and assumed equal population standard deviations is n - 1, where n is the number of paired differences.
Step-by-step explanation:
In a hypothesis test involving the difference between two population means when both of the population standard deviations are unknown and assumed to be equal, the degrees of freedom for the test statistic is n - 1, where n is the number of paired differences.