Typesetting LaTeX fraction terms to be larger in an equation

I have the following formula in LaTeX, based on Fisher's Exact Test. (NOTE: requires the use of the amsmath package for \binom.)

\begin{equation}
    P(i,j) = \sum_{x=|N(V_i) \cap V_j|}^{\min\{|V_j|, |N(V_i)|}
    \frac{ \binom{|V_j|}{x} \binom{|V - V_j|}{|N(V_i)| - x}}
    {\binom{|V|开发者_JAVA技巧}{|N(V_i)|}}
\end{equation}

This renders the fraction portion with very small, difficult to read text:

I would like my text more readable, as in the following example:

_{(source: plosone.org)}

What trickery can I use to get LaTeX to render my equation similarly?

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This may be what you're looking for:

\begin{equation}
    P(i,j) = \sum_{x=|N(V_i) \cap V_j|}^{\min\{|V_j|, |N(V_i)|} 
    \frac{\displaystyle \binom{|V_j|}{x} \binom{|V - V_j|}{|N(V_i)| - x}}
    {\displaystyle \binom{|V|}{|N(V_i)|}}   
\end{equation}

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Thought it might be good to add a reference:

A Guide to LaTeX2e, Kopka & Daly, 1995
Section 5.5 Fine-Tuning Mathematics
5.5.2 Selecting font size in formulas

In my edition, it's on pp 141-142, but this is out of stock on Amazon. The nearest Internet pointer I can find just now is here

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For fraction you can also use continued fraction \cfrac in combination with \left and \right.

Take a look here.

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Here's one idea.

In Preamble:

\def\mathLarge#1{\mbox{\LARGE $#1$}}

Then update your equation to:

\begin{equation}
    P(i,j) = \sum_{x=|N(V_i) \cap V_j|}^{\min\{|V_j|, |N(V_i)|}  
    \mathLarge{
        \frac{ \binom{|V_j|}{x} \binom{|V - V_j|}{|N(V_i)| - x}}
        {\binom{|V|}{|N(V_i)|}}
    }
\end{equation}

Results in:

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The following lines define three fraction commands with sizes intermediate between \displaystyle and \textstyle, in order of decreasing size:

\newcommand{\sdfrac}[2]{\mbox{\small$\displaystyle\frac{#1}{#2}$}}
\newcommand{\fdfrac}[2]{\mbox{\footnotesize$\displaystyle\frac{#1}{#2}$}}
\newcommand{\ltfrac}[2]{\mbox{\large$\frac{#1}{#2}$}}

See this page if further explanation is needed.