Like a lot of posters have already said, there's too many variables to establish a correct speed - type of bike, fitness of rider, terrain, tire pressures, gearing, rider mood, whether there's a full moon . . .

I would just concentrate on spinning and just ride, and not be concerned about speed right now.

Me? I maintain about 17 or 18 mph on a flat paved surface with no wind; but with lights, stop signs, everything else my rides actually average between 11.5 and 13 mph.