Dear SPMers<div><br></div><div>i am using ANCOVA to compare the differences between 2 groups.</div><div>since this is a genetic study, one of the genotype was relatively rare than another group.</div><div>in the first group, there are about 280 subjects</div>
<div>but in the second group, are was only 42 subjects...</div><div>i am wondering whether such unbalance design (280:42, about 5:1) would affect the statistical power or not?</div><div>(or maybe such unbalance sample size between groups is not&nbsp;acceptable?)</div>
<div>should i select and reduce my first group into about 84 subjects?</div><div><br></div><div>Best Regards,</div><div>Alan</div><div><br clear="all"><div><br></div>-- <br>--------------------------------------------------------------------------------------------------------------------------------------------------------------<br>
¶À·¡¤¤(Chu-Chung Huang)<br>Brain Connectivity Lab, <br>Institute of Biomedical Imaging and Radiological Sciences,<br>National Yang Ming University, Taipei, Taiwan<br>Tel: +886-2-28267000 Ext. 6134<br>Cell: 0932336606<br>
</div>