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Everyday Number Sense

A practical guide to the numbers around you

Everyday numbers arrive as prices, sizes, shares and rates. This guide gives the first check to make with each kind so you can read them accurately and calmly.

Averages and Percentages

Averages in daily life, explained from the start

An average condenses many values into one figure, and it turns up in prices, weather, travel times and grades. Learn what averages do well and what to ask about each one.

Averages and Percentages

Averaging percentages and where it goes wrong

Averaging several percentages can give the wrong overall figure when the groups differ in size. A weighted average, built from the underlying counts, gives the correct combined rate.

Reading Charts and Graphs

Checking the axes before you trust a graph

Before you believe a graph, check its axis labels, units, starting point and tick marks. These checks reveal many of the ways a chart can exaggerate a change.

Reading Charts and Graphs

Checklist for reading any chart you come across

Six checks, taken in a fixed order, help you judge any chart in a couple of minutes: its source, date range, scale, units, comparison and the claim it supports.

Tracking Your Own Data

Choosing what to measure in a personal log

Start a personal log with a clear question, then pick a few measures you can record consistently and explain why each one matters. Avoid tracking everything at once.
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