title: ggplot graph with two groups, each displaying their separate error bars
body: <p>I am trying to add error bars to my graph using <code>ggplot()</code>. Is there a way to add error bars for two groups in a <code>ggplot()</code> graph?</p>
  <p>I know that this code will give me error bars for one of my groups:</p>
  <pre><code>geom_linerange(aes(ymin=percentBias-normSEM, ymax=percentBias+normSEM),
          position = position_dodge(width = 0.05), col='red')
  </code></pre>
  <p>The dependent variable is percent bias (y-axis) and the x-axis displays the range of variability (1 to 8). I have two groups that I am graphing: Normal and Uniform. I would like to display both groups in the graph with their error bars, normSEM and uniSEM, respectively. Error bars are the standard error of the mean for each group. The code above applies the same error bars (normSEM) to everything.</p>