3. Standard Error. The smaller the Std-Err, the more powerful the test. There are three useful ways to reduce the Std-Err: a. The estimated OEC is typically a mean of large samples. As shown in Section 3.1, the Std-Err of a mean decreases proportionally to the square root of the sample size, so increasing the sample size, which usually implies running the experiment longer, reduces the Std-Err and hence increases the power.