There is a tool for everything. There are so many tools for so many different purposes that it is difficult to keep track of them. Here is one that tool that works well for a variety of analytical purposes, especially in helping to define and isolate problems to their root cause. This is called the Ishikawa Diagram, Fishbone Diagram and/or Cause-Effect Diagram. It can be easier to use a tool than describe how it is used, so interested readers might refer to Wikipedia for more details.
The function of this tool is to show the causes of an event or problem. The intention is to go beyond that and to identify “the fewest causes responsible for the most problems” – following the Pareto Principle. The consideration is that you also want to prioritize the tackling of problems according to how strongly they impact your business and profitability.
Simply, the idea is to define the major contributing parts of a “Cause” – which as Wikipedia shows, can vary according to the type of work you are doing. Customize this to your project. As it shows, the major parts associated with marketing are known as the 7 P’s – Product (or Service), Price, Place, Promotion, People, Positioning and Packaging.
Details are then added to each Cause. Where the type of machine being used by the end user can be a “cause for a problem” – you might have a long list of mobile devices. The extent of your testing could be a factor, suffice that your focus is on the devices in which your app is not working as intended. Listing all of those out might help define a common issue.
The Root-Cause Diagram itself should help you get pretty close to the problem, but is best used with The Five Why’s. The aim of asking, Why? Why? Why? Why? Why? Is to break a problem down until it cannot be broken down any further. The answer to those five why’s should help explain how the root cause of a problem can be effectively solved.
Wikipedia points out here that “people do not fail, processes do.” Perfect the process and you will get good results.
These tools and techniques work even better when part of a broader quality control and process improvement program – whether Lean, TQM, Six Sigma, or otherwise. Each has its nuances and their effectiveness is debated. Everything does not need to apply to the rigors of a full-fledged Black Belt project. Many of these things can be done on the fly, based upon priority, deadlines, budget, etc. When you apply to “the process” long enough on a variety of different projects, many problems are resolved before they ever happen.