Positive Control Method Select the method to use for computing the positive normalization factor. The methods are summarized in the following table: Method Description Geometric Mean The factor used for normalization is the geometric mean of the positive controls for each sample. Mean The factor used for normalization is the arithmetic mean of the positive controls for each sample. To Specify the Method to Use for Computing the Normalization Factor: Select the Positive Control radio button for Probe Normalization. Click the Positive Control Method drop-down menu. Click the desired method.