Passive Voice Usage in Undergraduate STEM Textbooks

The present study, a corpus-based quantitative analysis, investigated the use of passive voice in terms of percentage (percentage of total passive usage), constructions (the most commonly used passive forms), and dispersion (the verbs that tended to be associated with passive usage) in college STEM textbooks, more specifically in Science, Technology, Engineering, and Mathematics. The corpus consisted of twenty textbooks with over 1 million running words selected from the textbooks' chapters. By identifying the main verbs and passive verbs used in the textbooks, the percentage of passive voice usage was calculated. The statistical difference of passive constructions between disciplines was examined by conducting a MANOVA test, and an instrument, the Compleat Lexical Tutor was used to generate a word list of the most commonly-used past participles in passive voice. Results showed that the overall percentage of passive voice usage is over 30%. The MANOVA test revealed a statistically significant difference of passive voice constructions across the four disciplines, i.e. Science, Technology, Engineering, and Mathematics. Implications for teaching suggest that passive voice was an important grammar feature that needs to be taught tor the English as a second/foreign language students who major in the STEM fields. Additionally, the use of passive constructions should be taught differently in reading and writing based on the needs of the four STEM disciplines, due to the significant difference of passive forms usage in these fields.