This study developed a standard setting for Grade 11 of the Multimedia-based Assessment of Scientific Inquiry Abilities (MASIA) based on three levels of standard performance descriptions: below basic, basic, and proficient. The study also used a bookmark to identify the cut-off scores. Furthermore, the study discussed the correct degree of the MASIA standard, which depends on multiple levels of evidence, namely procedural, internal, and external evidence for validity. First, the result of the procedural evaluation for validity showed that the standard setting of scientific inquiry abilities adopted in this study is supported by the procedural evidence for validity. Second, the result of the internal evaluation for validity showed that the standard error of each performance level that participants reached in rounds one and two were within an acceptable range (standard error [SE] < 0.12), thus indicating good intra-rater consistency. The consistency within the standard-setting method was evaluated using the standard error of the sample mean based on the median of the cut-off scores from round two. The result showed that the standard error of every performance level was within an acceptable range (SE < 0.12), thus denoting high consistency within the results of the standard-setting method. Third, the inter-rater consistency of the standard setting was examined using an independent sample t test, and the results showed that none the cut-off scores set by the participants of different groups reached statistical significance. Therefore, the standard setting of scientific inquiry abilities can be supported by internal evidence for procedural validity. Finally, this study treated the quasi-setting results derived from the cluster analysis as convergent validity-based evidence to assess external validity. The results showed that the correlation coefficient of the three performance levels of the students differentiated by two standard-setting methods reached statistical significance, thus indicating that those who judged the performance levels of the students had a certain degree of consistency. Moreover, a discriminant analysis was conducted to determine the consistency of the standard settings, and the results revealed that the consistency of the factors classified into “observing and questioning,” “planning and experimenting,” “analyzing and concluding,” and “reasoning and arguing” were in the following sequence: 79.50%, 86.00%, 100.00%, and 89.90%. In the present study, the cut-off scores obtained by the bookmark presented high discrimination for each performance level category and can be supported using external evidence for validity. These results suggest that the bookmark standard setting of scientific inquiry abilities are appropriate and effective.