Two preeminent scholars on the clustering illusion, psychologists Daniel Kahneman and Amos Tversky, assert that the representativeness heuristic causes the clustering illusion, a cognitive shortcut where a small sample of data is assumed to be representative of the entire population that it’s pulled from.

The human brain’s ability to recognize patterns and draw conclusions is truly remarkable. However, remember to be cautious when using small sets of data to make assumptions about larger populations.

The representativeness heuristic can lead to the clustering illusion, where we mistakenly believe that a non-random pattern in a small subset of data is present throughout the entire sample.

It’s important to remember that random samples often contain more variability than we initially perceive. By acknowledging this tendency, we can approach data analysis with a more open mind and avoid drawing incorrect conclusions.

A classic example of this bias is the belief that if a coin toss results in “heads” several times in a row, “tails” is surely next. This is a fallacy because each coin toss is an independent event, and the odds remain 50/50 each time that it will be “heads.”

But how might we apply this to UX?

Suppose you’re analyzing user data in an e-commerce platform. Upon observing a few customers making purchases on consecutive days, you might perceive a clustering illusion, assuming that there is a pattern or preference for certain days of the week for online shopping. However, this apparent clustering might be purely coincidental, and there may be no actual preference for those specific days.

This bias leads us to overestimate the importance of these perceived clusters and causes us to overlook the overall randomness of the data set.