Use this text box to specify a control/reference level of the Treatment Arm . You must surround it in double quotation marks ( “” ).The level specified is used as the reference level for testing against other levels of the Treatment Variable in the Cochran-Mantel-Haenszel exact test to screen events or interventions for differences in incidence.If this field is left blank , the default level, when the data is in English, is "Placebo" or "Pbo" (case insensitive) when these are found.When neither "Placebo" nor "Pbo" are found or when the data are written in a language other than English, the default is set to the first sorted value. In these cases, you should avoid using the default control level. Instead, you should enter the control level term that matches your data to make sure the correct control level term is used.Note : You must type the character or numeric value exactly as it appears in the variable . You must enclose the value in double quotation marks ( “” ).