span class="co">##  </span></span>
<span><span class="co">## Summary:</span></span>
<span><span class="co">##               Group Obs Missing  Mean Std. Err. Std. Dev.         95% CI</span></span>
<span><span class="co">##    mri$sex = Female 369       4 130.9      1.79      34.3 [127.4, 134.5]</span></span>
<span><span class="co">##      mri$sex = Male 366       6 120.6      1.69      32.1 [117.3, 123.9]</span></span>
<span><span class="co">##          Difference 735      10  10.3      2.47      &lt;NA&gt;