Statistics exist to compress overwhelming data into usable meaning

Wheelan frames the entire discipline around one core function: taking mountains of raw, unmanageable data and condensing them into a single number or simple summary that a person can actually use to understand, compare, or decide something. A batting average, a poverty rate, a Gini coefficient measuring inequality — each is doing the same basic job of compression, trading detail for usability.

He's explicit that this compression is always a trade-off: every single-number summary necessarily discards nuance, and the real skill in statistical literacy is knowing what got left out, not just what the number says. A GPA, for instance, tells you almost nothing about how difficult someone's specific courses were.

This framing sets the tone for the whole book: statistics aren't about memorizing formulas, they're about learning to ask what any given number is actually capturing and what it's quietly ignoring.

Takeaway: whenever you see a single summary statistic, ask immediately what complexity it erased to get that simple.