Align left hand side of two tables

Question

Hi I am putting together a crib sheet and on it there are two tables of information that are separated by a paragraph or two of other text. Latex centres each table nicely, but because the tables have different widths the result looks odd on the page.

Is there a reasonably straight forward way to get the tables pretty much in the centre of the page, but with their left-hand side aligned?

Here is a cut down version of my code:

\documentclass[12pt]{article}
\usepackage[paper=a4paper,margin=1.75cm]{geometry}               
\usepackage{graphicx}
\usepackage{amssymb}
\usepackage{ragged2e}

\usepackage{fontspec,xltxtra,xunicode}
\usepackage{siunitx,amsmath}
\defaultfontfeatures{Mapping=tex-text}
\setromanfont[Mapping=tex-text]{Hoefler Text}
\setsansfont[Scale=MatchLowercase,Mapping=tex-text]{Helvetica}
\setmonofont[Scale=MatchLowercase]{Andale Mono}
\renewcommand\familydefault{\sfdefault}
\begin{document}
\thispagestyle{empty}
Content stripped out...


\subsubsection*{Statistics of small data sets $(N\le10)$}
\begin{table}[h]
\centering
\begin{tabular}{ll}
    Average                                   & $\overline{x}=\frac{x_1+x_2+\cdots+x_N}{N}$                       \\
    Range                                     & $R=x_{max}-x_{min}$                                            \\
    Uncertainty in a measurement & $\Delta x=\frac{R}{2}=\frac{R=x_{max}-x_{min}}{2}$             \\
    Uncertainty in the mean  & $\Delta \overline{x}=\frac{\Delta x}{\sqrt N}=\frac{R}{2\sqrt N}$ \\
    Measured value $x_m$                      & $x_m=\overline{x}\pm\Delta\overline{x}$                                 
\end{tabular}
\end{table}
\subsubsection*{Statistics of large data sets $(N>10)$}
When the data set is a sample of a larger set then a confidence interval is calculated:
% will have equations and table side-by-side

Content stripped out...

When the data set is complete then absolute statistics can be calculated:
\begin{table}[h]
\centering
\begin{tabular}{ll}
    Average                                   & $\overline{x}=\frac{\Sigma_{i=1}^N x_i}{N}$                                                \\
    Uncertainty in a measurement  & $\Delta x=\sigma=\sqrt{\frac{1}{N}\Sigma_{i=1}^N(x_i-\overline{x})^2}$                                    \\
    Uncertainty in the mean  & $\Delta \overline{x}=\frac{\sigma}{\sqrt N}$ \\
    Measured value $x_m$                      & $x_m=\overline{x}\pm\Delta\overline{x}$                                                          
\end{tabular}
\end{table}


\end{document}  

Cheers

Answer 1

You could use tabularx and specify a width for these tables:

\documentclass[12pt]{article}

\usepackage[paper=a4paper,margin=1.75cm]{geometry}               
\usepackage{graphicx}
\usepackage{amssymb}
\usepackage{ragged2e}

\usepackage{fontspec,xltxtra,xunicode}
\usepackage{siunitx,amsmath}

\usepackage{tabularx}
\begin{document}
\thispagestyle{empty}
Content stripped out\dots


\subsubsection*{Statistics of small data sets $(N\le10)$}
\begin{table}[h]
\centering
\begin{tabularx}{0.7\textwidth}{XX}
    Average                                   & $\overline{x}=\frac{x_1+x_2+\cdots+x_N}{N}$                       \\
    Range                                     & $R=x_{max}-x_{min}$                                            \\
    Uncertainty in a measurement & $\Delta x=\frac{R}{2}=\frac{R=x_{max}-x_{min}}{2}$             \\
    Uncertainty in the mean  & $\Delta \overline{x}=\frac{\Delta x}{\sqrt N}=\frac{R}{2\sqrt N}$ \\
    Measured value $x_m$                      & $x_m=\overline{x}\pm\Delta\overline{x}$                                 
\end{tabularx}
\end{table}
\subsubsection*{Statistics of large data sets $(N>10)$}
When the data set is a sample of a larger set then a confidence interval is calculated:

Content stripped out\dots

When the data set is complete then absolute statistics can be calculated:
\begin{table}[h]
\centering
\begin{tabularx}{0.7\textwidth}{XX}
    Average                                   & $\overline{x}=\frac{\Sigma_{i=1}^N x_i}{N}$                                                \\
    Uncertainty in a measurement  & $\Delta x=\sigma=\sqrt{\frac{1}{N}\Sigma_{i=1}^N(x_i-\overline{x})^2}$                                    \\
    Uncertainty in the mean  & $\Delta \overline{x}=\frac{\sigma}{\sqrt N}$ \\
    Measured value $x_m$                      & $x_m=\overline{x}\pm\Delta\overline{x}$                                                          
\end{tabularx}
\end{table}


\end{document} 

Answer 2

To align two center-set tables, they need to have the same widths. Currently, the left-hand columns of the two tabular environments appear to have the same width, whereas the right-hand column of the second tabular is wider than than of the first.

You could thus achieve your objective by issuing the instructions

\newlength\mylen
\settowidth\mylen{$\Delta x=\sigma=\sqrt{\frac{1}{N}\Sigma_{i=1}^N(x_i-\overline{x})^2}$}

in the preamble and using the instruction

\begin{tabular}{lp{\mylen}}

to start the first tabular. This will ensure that the second columns of both tables also have the same width.

A separate issue: You may want to think a bit more about the appearance of your document -- Helvetica text font and Computer Modern math font are not exactly well matched.