Mathematical and statistical open source software (OSS) has played a vital and positive role in computing statistics, performing numerical computations, and solving for real and complex scalars. There is an enormous need to apply quality models to this type of software. In this paper, we present an inclusive set of current quality models and demonstrate their application to OSS. As very little research has been carried out on the quality in use assessment of mathematical software, this work investigates the application of the quality in use model inspired by ISO/IEC 25010 on three OSS products: Scilab, R-Language, and GNU Octave. We can confidently state that Scilab, R-Language, and GNU Octave perform similarly in terms of effectiveness, efficiency, productivity, and cognitive load. However, Scilab outperforms GNU Octave slightly when it comes to error safety.