Common Errors in Statistics (and How to Avoid Them), 4th Edition

Glossary*

Accuracy and Precision. An accurate estimate is close to the estimated quantity. A precise interval estimate is a narrow one. Precise measurements made with a dozen or more decimal places may still not be accurate.

Deterministic and Stochastic. A phenomenon is deterministic when its outcome is inevitable and all observations will take a specific value. (These observations may be subject to measurement error.) A phenomenon is stochastic when its outcome may take different values in accordance with some probability distribution.

Dichotomous, Categorical, Ordinal, and Metric Data. Dichotomous data have two values and take the form “yes or no,” “got better or got worse.”

Categorical data have two or more categories such as yes, no, and undecided. Categorical data may be ordered (opposed, indifferent, in favor) or unordered (dichotomous, categorical, ordinal, metric).

Preferences can be placed on an ordered or ordinal scale such as strongly opposed, opposed, indifferent, in favor, or strongly in favor.

Metric data can be placed on a scale that permits meaningful subtraction; for example, while “in favor” minus “indifferent” may not be meaningful, 35.6 pounds minus 30.2 pounds is.

Metric data can be grouped so as to evaluate it by statistical methods applicable to categorical or ordinal data, but to do so would be to throw away information and reduce the power of any tests and the precision of any estimates.

Distribution, Cumulative Distribution, Empirical Distribution, and ...