Today software development is no longer an isolated work of a single programmer. Large systems are usually developed in a multi-language environment and run simultaneously on various platforms. Software development is a very complex process involving various factors. In this paper 32 environmental factors are defined and a survey was launched to investigate the impact of these factors on software reliability assessment. We extend our study by combining the original factors to reduce the dimension of the factor space; examine the impact of the environmental factors on the software reliability assessment improvement; investigate whether people have different opinions on ranking the environmental factors depending on their years of experience; and test the association between software reliability assessment improvement and participant's background information. Statistical analysis methodologies including factor analysis, linear regression, nested design, and chi-square test are utilized in this study.