This episode gives an explanation of how to develop and validate a quantitative instrument. No, you can't just make one up and send it out and get reliable results! This is a great basic overview of what it takes to make a valid and reliable scale/instrument for research purposes.

Dr. Cassandra Iannucci (@cassamariab) gives an overview of the process, more detailed information is available in the article. 

Iannucci, C., MacPhail, A., & R. Richards, K. A. (2018). Development and initial validation of the Teaching Multiple School Subjects Role Conflict Scale (TMSS-RCS). European Physical Education Review, 1356336X18791194.