What is a half-truth?
A half-truth contains a true core but nevertheless creates a false or incomplete impression. This can happen in two ways:
- True and false elements are mixed together.
- A statement is true in itself but omits decisive context.
Examples from everyday life
A mother asks her son why his brother is crying. He answers: “He fell down.” That may be true and still conceal the fact that he pushed him first.
The sentence “I did not meet Mr Unscrupulous with his wife on 14 January” leaves several possibilities open. Perhaps the meeting took place on another day. Perhaps his wife was not there. The compound statement can be true even though it obscures the crucial fact.
In the so-called Kennedy–Lincoln myth, true, inaccurate and invented details are strung together in such a way that a mysterious connection appears to emerge.
Half-truths in statistics
Statistical statements are particularly vulnerable to omitted context. A percentage can be numerically correct and still mislead if the denominator, time period, selection procedure or comparison group is missing.
Example: “Interest rates rose by two percent from 1 to 3 percent.” This formulation confuses percent and percentage points. The increase is two percentage points; relative to the initial value, the interest rate has tripled, which means an increase of 200 percent.
Likewise, “three is three times as much as one” is correct, while “three is three times more than one” is linguistically ambiguous. Precise wording prevents a correct number from creating a false idea.
Questions to ask
- What essential information is missing?
- What population does the number refer to?
- Is the stated relationship merely temporal, or also causal?
- Would the same statement still sound equally convincing with the full context?
Reference: Milo Schield: Statistical Prevarication: Telling Half Truths Using Statistics, Augsburg College, 2005.