Another question that tends to throw people is the one Dr. Herreid uses in the identify section of the exams. He is simply asking you what it means and what its significance is. All you have to say is that technically, it is sample size minus 1. It is more significant as degrees of freedom , a statistical value used in performing T-tests. Another thing to keep straight is Null hypothesis vs. Alternative hypothesis .
Null hypothesis states that the two samples are identical.
Alternative hypothesis states that the samples are statistically different.