| Problem |
Example |
| The conclusions do not follow logically from the evidence given. |
The candy bar was here on the table last night. This morning, it’s gone. Johnny must have taken it. |
| The argument is based on analogy that doesn’t work. |
Baseball bats can be as deadly as guns, but we don’t ban bats. |
| Fact and opinion are intermingled, opinions are presented as facts, or it is not clear which is which. |
People who regularly wear seatbelts are more responsible and have fewer accidents. |
| Celebrity is used as authority. |
Film star endorses new diet |
| Vague sources are used in place of specific references. |
"leading doctors say ... ," "science has shown that ... ," "compared to some other states ... ," "the scientific community recommends that ..." |
| Care is not taken to guard against deliberate or subconscious distortion, in self-reported opinions or information. |
“In a survey of our college students, 87% are rated as ‘above average.’” No notice is given that it was a self-reported survey with no outside confirmation. |
| No mention is made, in evidence said to come from an experiment, of control groups very much like the experimental group. |
Scientific studies proved that the new drug was effective for treating depression. |
| Graphs are used that distort the appearance of results. |
Chopping off part of the scale, using unusual scale units, or using no scale at all |
| Categories are over-generalized—implying that all members of a group have nearly identical characteristics. |
All "teenagers," "consumers," "immigrants" |
| Average results are reported, but not the amount of variation around the average. |
The average income of college graduates from private universities exceeds the average income of college graduates from public universities |
| A percentage or fraction is given, but not the total sample size. |
"9 out of 10 dentists recommend..." |
| Absolute and proportional quantities are mixed. |
“We had 3,400 more robberies in our city last year; whereas, other cities had an increase of less than 1 percent.” |
| Results are reported with misleading preciseness. |
Representing 13 out of 19 students as 68.42 percent. Using the percentage distorts the fact that the actual sampling is a very small number. |
| Explanations or conclusions are represented as the only ones worth consideration, with no mention of other possibilities. |
The experimental data prove that aluminum is the best conductor (when only 3 conductors were tested). |