Reader Joel Wiles points out that one of Barack Obama’s latest fundraising emails presents a little case study in the use of misleading statistical comparisons:

In February alone, more than 94% of our donors gave in amounts of $200 or less. Meanwhile, campaign finance reports show that donations of $200 or less make up just 13% of Senator McCain’s total campaign funds, and only 26% of Senator Clinton’s.

…Senator McCain has raised more than 70% of his total campaign funds from high-dollar donors giving $1,000 or more. Senator Clinton has raised 60% of her funds from $1,000-and-up donors.

These two sets of figures are non-comparable. Even though 94% of Obama donors gave less than $200, a large proportion of his funds are still likely to come from high dollar donors. Conversely, even though McCain and Clinton have raised a large proportion of their total funds from high dollar donors, a high percentage of their donors might have given less than $200. Obama’s numbers are likely to be less skewed than McCain’s or Clinton’s but we don’t know because he never gives us the relevant comparison.