title: R lme4 nested fixed effects. Do I nest as random effects?
body: <p>I am currently fitting model in glmer (although the same question applies to lmer).</p>
  
  <p>However I have two (what I think are) nested fixed effects. I am testing how long people spend eating compared to their sex and weight. Obviously how heavy someone is depends on their sex (the distribution of weights is different between the sexes), but I care about this in my model.  I want to test whether the heaviest women eats more than the lightest women and the heaviest man eats more than the lightest man, but I want one model to see if there is a population wide effect.</p>
  
  <p>This is how I thought of doing it by having the two fixed effects also as nested random effect:</p>
  
  <pre><code>model &lt;- glmer(TimeEating ~ Sex + Weight + (1|Sex:Weight), 
        data, family = poisson(link = "log"))
  </code></pre>