About presentation precision

Statistics are often presented to more decimal places than necessary. Many statistical software packages make the mistake and present statistics to 7 or more significant figures, believing it suggests the results are more precise.

Internally Analyse-it calculates all statistics to a high precision (see Calculation precision), but presenting them to too many decimal places is misleading and gives a false sense of precision, especially when the source variables are not observed at such precision. It would, for example, be pointless to present the mean of height to 7 decimal places when the height was observed only in whole centimetres. In this case presentation to one decimal place would be sufficient and would not incorrectly lead the reader to believe height was measured to millionths of a centimetre.

To avoid misleading readers, Analyse-it presents statistics only to a sensible number of decimal places. For most statistics the presentation precision is based on the Excel number format applied to the cells containing the source data. For example, sums are presented to the same number of decimal places as the source data, means, variances,and standard deviations are presented to one additional decimal place, standard errors to two additional decimal places.

To control how statistics are presented apply a number format to the source data (see Setting observation precision).

NOTE If the default Excel Number Format General is applied to the observations Analyse-it will scan the observations and automatically determine the number of decimal places used.

Part of the Analyse-it for Microsoft Excel user guide. For more information about Analyse-it, the statistics add-in for Microsoft Excel, or to download a free 30-day trial please visit http://www.analyse-it.com/. © Analyse-it Software, Ltd. Analyse-it® is a registered trademark. Microsoft® Excel® is a registered trademark of Microsoft.