Answer:
This means that by itself, the correlation doesn't say if more exercise causes longer sleep.
Explanation:
Jake has found a correlation in between the sleeping hours at night and the number of the time one spends on the exercising. He observe that longer he he spend exercising the more hours he spend in sleeping in night, however there is no scientific evidence that is explained by his psychology instructor that there is no cause and effect mean to this correlation.
Thus, the correct answer is : by itself, the correlation doesn't say if more exercise causes longer sleep.