Set parameters are entered into the dyno for calculations (gear ratio - final drive - etc)
Once the dyno operator get the wheels moving, he puts the car in a set gear (normal 4th at a 1:1 ratio {Contour is 1.03:1}) and accelerates from a set rpm to redline. (I.E. 3000rpm to 7000rpm)
You could run in any gear technically, but the results would be significantly more skewed (larger error margin) the further you get from a true 1:1 ratio. (the dyno's computer is doing more calculating verses using it's own sensor data)
