Re: precision of a measurement (documentation related question)

*To*: mathgroup at smc.vnet.net*Subject*: [mg61607] Re: precision of a measurement (documentation related question)*From*: Chris Chiasson <chris.chiasson at gmail.com>*Date*: Sun, 23 Oct 2005 05:46:21 -0400 (EDT)*References*: <acbec1a40510221346r2cee06c3led071a9eeb92d58b@mail.gmail.com> <acbec1a40510221456i64c176d7s73cd5110ac614ba1@mail.gmail.com> <acbec1a40510221537h4df0a645h1824fdb52b9f54b@mail.gmail.com>*Sender*: owner-wri-mathgroup at wolfram.com

Can someone explain: Interval@Sig[30,0.5]//FullForm Interval at Sig[0.183,0.0005]//FullForm Notice how the interval seems to be correct for 30+ or - 0.5, but not for 0.183 + or - 0.0005 On 10/22/05, Chris Chiasson <chris.chiasson at gmail.com> wrote: > To follow up, here is a function that people could use to compactly > enter in measurements and their (half) error range to obtain a number > in Mathematica that will have the appropriate significance attached to > it (no, I haven't really thought of handling complex numbers yet, but > I am sure someone smarter than myself could extend it). > Sig[x_,dx_]:=SetPrecision[x,-Log[10,Abs[dx/x]]] > > Following my previous question: > Sig[30,0.5] > is the answer I was looking for earlier. > > This Sig function could be combined with the Notation package to make > input even more tidy looking. One could also write a Notation to make > numbers with significance show error ranges by default... > > Regards, > > On 10/22/05, Chris Chiasson <chris.chiasson at gmail.com> wrote: > > Thanks to a Mention by Maxim in this thread: > > http://groups.google.com/group/comp.soft-sys.math.mathematica/browse_frm/thread/1768e67ba5ac75f3?tvc=1&q=interval+significance > > and the documentation for Interval, > > I was able to figure out the answer to my question: > > FullForm@Interval[SetPrecision[x,-Log[10,dx/x]]]/.{{x\[Rule]30, > > dx\[Rule]0.5},{x\[Rule]30,dx\[Rule]1} > > > > On 10/22/05, Chris Chiasson <chris.chiasson at gmail.com> wrote: > > > Hi Mathgroup, > > > If I know that a number (say in inches, measured on a ruler that only > > > has marks for inches) and its error are: > > > 30 + or - 0.5, > > > then looking at the help file for Precision, I see that the precision is: > > > -Log[10,dx/x] > > > In this case, is dx = 0.5 or is it equal to 1.0?? > > > I have noticed that in either case, the number of significant > > > digits/the precision is less than 2. > > > > > > Your thoughts? > > > -- > > > Chris Chiasson > > > http://chrischiasson.com/contact/chris_chiasson > > > > > > > > > -- > > Chris Chiasson > > http://chrischiasson.com/contact/chris_chiasson > > > > > -- > Chris Chiasson > http://chrischiasson.com/contact/chris_chiasson > -- Chris Chiasson http://chrischiasson.com/contact/chris_chiasson