Internally Analyse-it uses double-precision (15 significant digits) in all calculations. For greater accuracy Analyse-it also uses it's own distribution and statistical functions and does not use any mathematical or statistical functions provided by Excel. This ensures the statistics in Analyse-it are computed to a high-degree of precision.
Some commentators claim Microsoft Excel is unsuitable for statistical analysis. In early versions of Excel the built-in Excel functions such as STDEV were unreliable and add-ins using such functions produced unreliable results. Because Analyse-it does not use any of these functions, and only uses Excel for data-entry and reporting, it is not affected by these problems.