This makes sense because I have seen commercials that say things like "4 out of 5 dentists recommend this toothpaste" and only 4 dentists are hired to state their opinion on the matter. Also, when looking at multiple variables and collecting data on each of them, as well as extra data that isn't really needed or used for the experiment-- especially when utilizing surveys-- erroneous conclusions can be drawn. An example being: if the researcher is looking for what increases depression in individuals and they collect data on hair length and coffee drinking, they might link the two in a statement like= "People with longer hair are less likely to drink coffee."