The seven deadly sins of statistical misinterpretation, and how to avoid them

A focus on a "normal distribution," - also known as a "bell curve," is where most people are near the average score, and only a small group is far above or below average. However, when you're dealing with extremes, small group differences can matter a lot.

Although a small change in performance makes no difference to the whole, the fluctuations change the character of the extremes.

Just because two things change at the same time, or in similar ways, does not mean they are related.

Question the observed association. Are there many occurrences, or is this merely chance? Can you predict future associations?

When two things are related, one might be tempted to see a causal path. For instance, that mental health problems lead to unemployment. It is possible that it is reversed, such as unemployment, causing mental health issues.

When you think about the association, ask if the reverse is possible, or even if it could go both ways, creating a feedback loop.

We sometimes forget to consider "third factors," or outside causes, that could be the link between two things, because both are actually effects of the third factor.

Avoid this error by always considering more factors when you see a correlation.

A graph maker may choose a small range of a larger graph to highlight a little difference or association and make it look more significant.

Take care to note the graph's labels along the axes. Question unlabelled graphs.