Editing False precision (section)

==Overview==
[[Madsen Pirie]] defines the term "false precision" in a more general way: when exact numbers are used for notions that cannot be expressed in exact terms. For example, "We know that 90% of the difficulty in writing is getting started." Often false precision is abused to produce an unwarranted confidence in the claim: "our mouthwash is twice as good as our competitor's".<ref>{{cite book|last1=Pirie|first1=Madsen|title=How to Win Every Argument: The Use and Abuse of Logic|date=2015|publisher=Bloomsbury Publishing|pages=78–80|isbn=9781472526977|url=https://books.google.com/books?id=YMPuBQAAQBAJ&pg=PT78|access-date=22 October 2015}}</ref>

In [[science]] and [[engineering]], convention dictates that unless a [[margin of error]] is explicitly stated, the number of [[significant figures]] used in the presentation of data should be limited to what is warranted by the precision of those data. For example, if an instrument can be read to tenths of a unit of measurement, results of calculations using data obtained from that instrument can only be confidently stated to the tenths place, regardless of what the raw calculation returns or whether other data used in the calculation are more accurate. Even outside these disciplines, there is a tendency to assume that all the non-zero digits of a number are meaningful; thus, providing excessive figures may lead the viewer to expect better precision than exists.

However, in contrast, it is good practice to retain more significant figures than this in the intermediate stages of a calculation, in order to avoid accumulated [[rounding error]]s.

False precision commonly arises when high-precision and low-precision data are combined, when using an [[electronic calculator]], and in [[conversion of units]].