Derrick just got home from playing soccer on a muddy field. He is curious how different brands of laundry detergent compare in removing mud from clothes, so he sets up an experiment.

In one laundry load, he puts his muddy socks with Brand A detergent. In the next load, he puts his muddy jersey with Brand B detergent. In the final load, he puts his muddy shorts with Brand C detergent.

Afterward, he noticed that the jersey came out the cleanest. He concludes that Brand B is the best detergent for removing mud from clothes. Is his conclusion valid?

Question

Derrick just got home from playing soccer on a muddy field. He is curious how different brands of laundry detergent compare in removing mud from clothes, so he sets up an experiment. 

In one laundry load, he puts his muddy socks with Brand A detergent. In the next load, he puts his muddy jersey with Brand B detergent. In the final load, he puts his muddy shorts with Brand C detergent. 

Afterward, he noticed that the jersey came out the cleanest. He concludes that Brand B is the best detergent for removing mud from clothes. Is his conclusion valid?

rsmith6559 · Answer

In principle, yes.  But there are a bunch of variables that haven't been considered.

scign · Answer

rsmith6559 is right:
- Are there any other garments in each load?
- Are the garments in the experiment equally muddy?
- Were the garments equally clean before the soccer match?
- Are the amounts of each brand used proportional to the load?
etc...

specter0420 · Answer

No, he needs more controls. To many variables.