Statistics Section 1.3 notes

Uses and Abuses of Statistics

Bad Samples – the use of inappropriate methods to collect data One example of a bad, but very common, collection method is a self-selected survey. This is one in which the respondents themselves decide whether or not to be included in the survey. Examples – answering a mail survey, calling in to respond to a poll, answering an online poll.

Small samples – making broad conclusions based on samples that are far too small. Example – “Four out of five dentists surveyed…” when only five dentists were surveyed…small sample size.

Loaded questions – Survey questions are worded to elicit the desired response. Example: Should students be allowed to go out for lunch? Should students be allowed to leave campus for lunch which adds to afternoon traffic, requires additional police patrol, and leads to more student tardies?

Misleading graphs – Many visual devices such as bar graphs and pie charts can be misleading if people only examine the shape without looking at the numerical information provided. Pictographs – drawings of objects may be misleading. Artists can create false impressions that distort differences.

When trying to get out of being issued a ticket, most drivers tell law enforcement officers they missed the sign; 17% cry and 11% claim to feel sick.

Precise numbers – When a statement includes a very precise figure, people incorrectly assume it is accurate. It is better to use an estimate. Example – There have been 5,354,987 babies born in the United States this year. That number changes constantly. Better to say about 5.4 million babies.

Distorted percentages – Misleading or unclear percentages are sometimes used. Partial pictures – not presenting the complete story Deliberate distortions – lying on purpose!