I'm looking for a resource of existing System Usability Scale (SUS) study results to compare against.
I've read in a few papers/webpages that plenty of such data is available, unfortunately I can't seem to find any immediately.
I could probably find separate papers with separate results, but I got the impression they were talking about databases.
Are there any resources which compile SUS study results and optionally allow you to access it by category?
The take-home I get from Bangor, Kortun, & Miller (2009) that you cite in your comment is that there’s not much difference at least in the categories they used –all averaged in the 66-76 range, while individual product scores ranged from 30 to 94. With the quartile scores Bangor et al provide, you can convert a score you have into a percentile by making some assumptions of the distribution. Or, to make it easier, use Jeff Sauro's percentile converter and guide for SUS.
I'm not so sure breaking products down into more specific categories will yield a wide range of averages. Form factor (e.g., TV versus phones) influences usability, but I’d expect smaller average differences among functional categories within each form factor (e.g., ecommerce versus social networking on the web). If you wanted a database, the first step would be to define subcategories of products that are correlated with usability. That itself is a pretty big research project.
If you really need to know precisely where your product stands with respect to your competition, then run your own SUS test on the competition using the same user pool, tasks, and testing environment as you run on your own product.
I think the SUS has more value as a benchmark that you set for the product and try to improve on, rather than compare against a competitor's product. This is because different products will have different strengths and weaknesses, and the SUS just doesn't provide enough detail for you to make in-depth analysis. If there's anything that seems to be a reoccuring theme in usability studies and analysis, then it is that every user and product is different, and we can't take anything for granted. However, there's no better place to start than from your own products and try to understand it better before working out your competitors.
