Reversed by Data

Imagine a hospital that boasts a higher overall survival rate than its competitor, yet when you look closely, the competitor is actually better at treating every single individual disease. This is not a clerical error or deliberate fraud; it is a terrifying mathematical reality that routinely sabotages medical studies, corporate analytics, and public policy. Simpson's Paradox occurs when a clear trend appears in multiple different groups of data, but completely disappears or reverses when those groups are combined. It exposes a massive vulnerability in how the human brain processes statistics. We are biologically wired to assume that combining truthful sub-sets of data will yield a truthful aggregate, but hidden variables can flip the entire meaning of the numbers, turning a definitive "yes" into a catastrophic "no." This book is a deep dive into the invisible traps of modern data consumption. You will explore historical cases where prestigious universities were falsely sued for gender bias, and how marketers actively exploit this paradox to make failing products look like bestsellers. Stop taking charts and aggregates at face value. Master the analytical tools to spot lurking variables, decode statistical illusions, and protect your decision-making from the deceptive nature of combined data.