"The same set of statistics can produce opposite conclusions at different levels of aggregation." is a quote useful in teaching about Simpson's Paradox from American Economist Thomas Sowell (1930 - ). The quote may be found on page 102 of his 1996 book The vision of the Anointed: Self-Congratulation As a Basis for Social Policy. The quote may also be found at the science history website www.todayinsci.com.