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

TABLES

Is text, a table, or a graph the best means of presenting results? Dyke [1997] would argue that “Tables with appropriate marginal means are often the best method of presenting results, occasionally replaced (or supplemented) by diagrams, usually graphs or histograms.” van Belle [2002] warns that aberrant values often can be more apparent in graphical form. Arguing in favor of the use of ActivStats^® for exploratory analysis is that one can so easily go back and forth from viewing the table to viewing the graph. In any event, a picture is worth a 1000 words only if it doesn’t take more than 1000 words to explain.

A sentence structure should be used for displaying two to five numbers, as in “The blood type of the population of the United States is approximately 45% O, 40% A, 11% B, and 4% AB.”⁴ Note that the blood types are ordered by frequency.

Marginal means may be omitted only if they have already appeared in other tables.⁵ Sample sizes should always be specified.

Among our own worst offenses is the failure to follow van Belle’s advice to “Use the table heading to convey critical information. Do not stint. The more informative the heading, the better the table.”⁶

Consider adding a row (or column, or both) of contrasts. “For example, if the table has only two rows we could add a row of differences, row 1 minus row 2; if there are more than two rows, some other contrast might be useful, perhaps ‘mean haploid minus mean diploid’, or ‘linear component of effect of N-fertilizer’.” ...