This study investigated whether background knowledge and methodological beliefs affected students'' interpretation of volume and temperature data for an ideal gas. To this end, we provided 22 pre-service science teachers with real measurement data and asked them to derive the relationship between the two variables. First, the pre-service teachers (hereafter referred to as students) were divided into two groups; one was given information about the variables, and the other was not. When information on the variables was provided, more students were able to propose a relationship consistent with their background knowledge, indicating that background knowledge affected the interpretation of data. Secondly, to examine the influence of methodological belief, we used Likert-scale questions to determine whether students considered a simple scientific law or an accurate law to be better. We found that they tended to suggest a relationship in a manner consistent with their methodological beliefs. Based on these results, further research is proposed to investigate the effect of other possible methodological beliefs on scientific inquiry.