In an experiment to determine the effects of varying inlet water flow rate on the HTU (in.) for the cross-flow, pilot-scale cooling tower, different lab groups used the same water flow rates to yield...

In an experiment to determine the effects of varying inlet water flow rate on the HTU (in.) for the cross-flow, pilot-scale cooling tower, different lab groups used the same water flow rates to yield the following results:

Is the difference in HTU due to group differences or flow rates?