Statistical Literacy: Reading Tables of Rates and Percentages

Statistical literacy depends on the ability to read and compare data presented in tables and graphs. Tables of rates and percentages are very useful in supporting arguments, but these tables are often difficult to decode. This paper presents rules for determining whether an index variable in such a table is part or whole depending on whether the associated margin value is an average, a sum or a 100% sum. Tables with missing margin values – date-indexed tables, half tables and control tables – are analyzed. Recommendations are made to improve reader understanding of any table involving rates or percentages.