A ball in flight is recorded and analyzed using digital video analysis software. The analysis produced the result that the ball had a horizontal speed of 1.20 m/s. In the analysis, a stick was used as a calibration standard, and it was believed that the stick was 1.0 m long. However, after the analysis was done, it was discovered that the stick was actually 0.70 m long.

Hmm, your question?

The real speed of the ball?

Well, if so, you know the 'analysed' speed and the 'assumed distance'. You can find the actual time taken, since that cannot be false.

Then, you know the real distance and real time taken, find the real speed.

Both making use of the formula and rearranging correspondingly.