I once worked at a major big box retailer where somebody came up with a visualization that purported to show, for a given product category, purchases made in other categories. One surprising purchase correlation was customers bought TV stands after buying DVD players. So, this nugget was trumpeted at countless meetings about the value of big data analytics. Multiple marketing campaigns were designed around this discovery.

Of course, that made no sense, so I checked a little deeper. You know what else people also buy when they buy DVD players? TV's. The DVD/furniture relationship was an artifact of the high degree of correlation between TV's and DVD players, which the visualization tool failed to account for.

I brought this up immediately, but received tepid response. Of course, months later, I was still hearing about DVD players and furniture. It had become part of the institutional lore, and no facts were going to replace that.