There are a variety of ways one could approach this. My proposal would be to go to the putlldown menus and select Tables==>Summary. There you select the 20 different collumns of data and specify to calculate the mean of each column. It will create a new table with one row, which will have one column for each input column. Then, a new column can be added for each of the columns, and then specify a formula for each column, which makes the comparison to see if the reference std is greater than the absolute difference between the calculated mean and the reference mean.
Rather than doing separate calculations I would add a step that would allow the calculation to only have to be specified once. What I would do, is once the summary data table is created, I would then go to Tables==>Stack and stack all of the summary columns. Once this is done, only a single additional column would have to be created to determine if the reference std was greater or less than the difference .
Jim