Hi yt770,
To answer your immediate question: YES - a poor night's sleep could absolutely impact your performance to such a degree as to significantly decrease your overall score. The severity of the score drop will obviously depend on the individual, but there are a number of other factors that you also need to consider. First, how closely did your 'practice routine' match up with what you faced on Test Day? Did you take your CATs at the same time of day as your Official GMAT? Did you take them
...
To answer your immediate question: YES - a poor night's sleep could absolutely impact your performance to such a degree as to significantly decrease your overall score. The severity of the score drop will obviously depend on the individual, but there are a number of other factors that you also need to consider. First, how closely did your 'practice routine' match up with what you faced on Test Day? Did you take your CATs at the same time of day as your Official GMAT? Did you take them
...
