An ideal answer to this question will demonstrate that you are capable of monitoring a situation as it evolves.

For example:

Whilst working in a call centre as a supervisor, I introduced 'Sugar Fridays' - giving my team sweets and treats to get them through the Friday slog.

Prior to introducing the incentive, I compiled a backlog of sales figures from previous Fridays. I then introduced the incentive on a trial period, continued collecting data and cross-compared the results. There was an obvious peak in sales figures and so the incentive became permanent.