Answer
``Significantly different at the 0.01 level'' means that out of every 100 samples, you would expect less than one of them to have this large of a difference in the number of total artifacts if they were really the same number. Since it is so rare to have this large difference, it is reason to suspect that the mean number of artifacts of grave sites containing pig skulls is much larger than the mean number of artifacts for grave sites without pig skulls.
Work Step by Step
``Significantly different at the 0.01 level'' means that out of every 100 samples, you would expect less than one of them to have this large of a difference in the number of total artifacts if they were really the same number. Since it is so rare to have this large difference, it is evident to suspect that the mean number of artifacts of grave sites containing pig skulls is much larger than the mean number of artifacts for grave sites without pig skulls.
