title: Anova with count data: glm?
body: <p>I have this kind of data:</p>
  
  <blockquote>
    <p>y: count data <BR>x: a factorial predictor with 3 levels</p>
  </blockquote>
  
  <p>Conceptually I need an ANOVA testing if the means of <code>y</code> for the three levels (<code>group</code>) are significantly different.
  Due to the <code>y</code> is a count I performed a poisson <code>glm</code> like this (in R):</p>
  
  <pre><code>y (count) ~ glm(x, family=poisson)
  </code></pre>
  
  <p>and then? How can I proceede?
  I need to know if level <code>1</code> is significantly different from <code>2</code> and <code>3</code> and if <code>2</code> is significantly different from <code>3</code> (all the possible combinations).</p>
  
  <p>Thanks</p>