The company behind the BioNomial app has hired you to do an experiment to show that their app increases fitness more than their free competitor. You are concerned that various other factors, such as age, gender, amount of working out already done by users of the app, and simply competitive nature (competitive people will work harder during the experiment) may drown out results. Use the buttons on the side to simulate various versions of the experiment and see what happens in different designs.
One set of volunteers has been randomly generated for you, and a completely randomized design has been simulated. Click 'Randomize treatments and run experiment' to re-assign volunteers randomly and run again, changing blocking choices if you want. (Remember - in the real world you would only get one shot!). You can also click 'Generate Volunteers' to get an entirely new population.