Apples to Oranges. When raw numbers are used, or compared to percentages - beware. Percentages usually convey more information than raw numbers. For example, in the 90s conservatives said crime was increasing because there were more murders. In fact, since the population increased by more, there was actually a decrease in the rate of crime - the percentage of the population murdered went down.

Odd number ranges. When an unusual period is used, beware that this may show a blip in a long term trend. If climate data from 1983 - 1996 is used, ask why they don't use round numbers, such as 1980-1990 or 1980-1995.

Coincidence passed off as cause and effect. "If the number of people buying ice cream at the beach is statistically related to the number of people who drown at the beach, then nobody would claim ice cream causes drowning because it's obvious that it isn't so (no more than drowning causes ice cream buying). Replace "ice cream" by the technical name of a chemical the public is not familiar with, and "drowning" by cancer, and immediately you can have many people believe you." See Onpedia.

Attributing an existing trend to some new law. The decline in the crime rate in California is said to be due to 3 Strikes, since the crime rate declined after 3 strikes was passed. However, the crime rate started to decline before 3 strikes was passed. 3 Strikes

Absolute numbers vs. percentages. Say that crime has been increasing for years. A gun control bill is passed, and crime continues to rise, but at a slower rate. Commentators say that crime rose after the bill was passed, thus it didn't work.

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