 defines the shape of the distribution.
          </p>
<p>
            For example, the binomial distribution probability distribution function
            (PDF) is written as <span class="serif_italic"><span class="emphasis"><em>f(k| n, p)</em></span>
            = Pr(K = k|n, p) = </span> probability of observing k successes out
            of n trials. K is the <a href="http://en.wikipedia.org/wiki/Random_variable" target="_top">random
            variable</a>, k is the <a href="http://en.wikipedia.org/w