Want to know how we did it?
Step 1. Understand the experiment
The description text of E-MTAB-3420 and the sample attributes indicate that skeletal muscle tissue was taken from patients with diabetes and healthy individuals in order to identified gene sets associated with insulin resistance. Thus, the experimental variable in E-MTAB-3420 is "disease" and the two conditions that are compared are "diabetes mellitus" and "normal".
Step 2. Download and open SDRF
To download and view the SDRF file, click on the link on bottom of the experiment page under "Files" and select "E-MTAB-3420.sdrf.txt". If your browser opens the text file directly, chose the option to save the page/file in the browser menu. Alternatively, use right-click on the link "Save link/file as…". Go to your downloads folder and open E-MTAB-3420.sdrf.txt, using right-click "Open with…" and choose your favourite spreadsheet software.
Step 3. Group files
Find the columns "Factor Value[disease]" (the last column) and "Array Data File" (the third last column). Now you should be able to categorise the data files according to the disease condition. The correct annotation of the raw data files is essential for any type of analysis.